diff --git a/CHANGELOG.md b/CHANGELOG.md
index beaba29..f9f9469 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # Changelog
 
+## 2026-05-07 17:37 CEST — feat(go): M5.1 — /api/* wire types + JSON Schemas
+
+- New `go/internal/web/api/` package: `AdultsResponse`, `JuniorsResponse`, `PaymentsResponse`, `VersionResponse` with explicit `json:` tags matching Python view-model keys.
+- `Expected{Value int; Unknown bool}` custom `MarshalJSON` emits integer or `"?"` for junior single-attendance months.
+- `schemagen_test.go` golden-tests four JSON Schemas committed to `go/tests/fixtures/api-schema/`. `JSONSchema()` on `Expected` lives in the test file — production binary has no jsonschema dep.
+- PR #16.
+
 ## 2026-05-07 15:26 CEST — refactor(app): extract view-model builders into scripts/views.py
 
 - Pulled ~350 lines of inline per-row computation out of `adults_view`, `juniors_view`, and `payments` into three pure functions in `scripts/views.py`: `build_adults_view_model`, `build_juniors_view_model`, `build_payments_view_model`.
diff --git a/docs/plans/2026-05-03-2349-go-backend-rewrite-progress.md b/docs/plans/2026-05-03-2349-go-backend-rewrite-progress.md
index 4ed759d..b8f14e3 100644
--- a/docs/plans/2026-05-03-2349-go-backend-rewrite-progress.md
+++ b/docs/plans/2026-05-03-2349-go-backend-rewrite-progress.md
@@ -97,7 +97,7 @@ Goal: every external IO (Sheets, Drive, Fio, file cache) accessed through a narr
 
 Goal: byte-equal JSON between Python and Go for every route. This is the parity contract.
 
-- [ ] **M5.1** Hand-author Go structs for `/api/adults`, `/api/juniors`, `/api/payments`, `/api/version` with explicit `json:` tags matching Python keys; emit JSON Schemas via `github.com/invopop/jsonschema` to `tests/fixtures/api-schema/`
+- [x] **M5.1** Hand-author Go structs for `/api/adults`, `/api/juniors`, `/api/payments`, `/api/version` with explicit `json:` tags matching Python keys; emit JSON Schemas via `github.com/invopop/jsonschema` to `tests/fixtures/api-schema/` — `f253e3f`
 - [ ] **M5.2** Implement Go handlers for `/api/*` routes composing `services/*` results into the JSON structs
 - [ ] **M5.3** Add Python `/api/X` shadow endpoints in [app.py](app.py): `jsonify(view_model_dict)` — no transformation
 - [ ] **M5.4** Build `cmd/parity/main.go`: hits both backends' `/api/X`, normalizes allowlist (`render_time.total`, `build_meta`), prints `cmp.Diff`. Add `make parity` target
diff --git a/docs/plans/2026-05-07-1650-go-rewrite-m5-1-api-structs-schemas.md b/docs/plans/2026-05-07-1650-go-rewrite-m5-1-api-structs-schemas.md
new file mode 100644
index 0000000..5c6b097
--- /dev/null
+++ b/docs/plans/2026-05-07-1650-go-rewrite-m5-1-api-structs-schemas.md
@@ -0,0 +1,240 @@
+# M5.1 — Hand-author Go API structs + emit JSON Schemas
+
+Companion to:
+- [2026-05-03-2349-go-backend-rewrite.md](2026-05-03-2349-go-backend-rewrite.md) (master design)
+- [2026-05-03-2349-go-backend-rewrite-progress.md](2026-05-03-2349-go-backend-rewrite-progress.md) (progress tracker — M5.1 row)
+- [2026-05-07-1431-m5-json-api-parity.md](2026-05-07-1431-m5-json-api-parity.md) (Python view-model extraction prep — already merged as `b562ce3` / `32a16ff` / `59223c0`)
+
+## Context
+
+M4 (IO layer behind interfaces) just landed. M5 is the JSON-parity contract phase — byte-equal JSON between Python and Go for `/api/adults`, `/api/juniors`, `/api/payments`, `/api/version`. Within M5, the work splits four ways:
+
+- **M5.1 — this plan.** Define the wire contract: hand-authored Go structs with explicit `json:` tags matching Python keys, plus committed JSON Schemas generated by `github.com/invopop/jsonschema`. **Schemas only — no handlers, no Python `/api/X` routes, no parity tool.**
+- M5.2 — Implement Go handlers that compose `services/*` results into these structs.
+- M5.3 — Add Python `/api/X` shadow endpoints in [app.py](app.py).
+- M5.4 — `cmd/parity/main.go` + `make parity` target.
+
+The recent Python view-model extraction (`scripts/views.py`) lays the groundwork: every Python builder now returns a plain dict that an `/api/X` shadow can `jsonify` (with one minor unwrap step — see decision #1 below). M5.1 is the matching Go side: types and schemas that pin down the contract before any code writes JSON to a wire.
+
+## Key design decisions
+
+1. **Wire format is nested objects, not strings-of-JSON.** The Python view-model dicts contain three template-only fields that are pre-serialized JSON strings: `member_data`, `month_labels_json`, `raw_payments_json`. Those exist purely to feed inline `<script>` blocks in Jinja templates ([scripts/views.py:227-237](scripts/views.py#L227-L237)). The `/api/X` JSON contract uses the **un-stringified** nested form. Rationale:
+   - The master design doc references `total_balance`, `original_expected`, `attendance_count` as struct fields ([2026-05-03-2349-go-backend-rewrite.md:223-225](docs/plans/2026-05-03-2349-go-backend-rewrite.md#L223-L225)), which are *inside* `member_data` — only meaningful if it's a nested object.
+   - The `Expected` `MarshalJSON` design (emit `42` or `"?"`) ([same doc:233-238](docs/plans/2026-05-03-2349-go-backend-rewrite.md#L233-L238)) only fires inside `member_data`; pointless if that field is a string.
+   - Strings-of-JSON make `invopop/jsonschema` schemas useless for those fields (`{"type": "string"}` describes nothing).
+   - The Python prep plan ([2026-05-07-1431-m5-json-api-parity.md:87-89](docs/plans/2026-05-07-1431-m5-json-api-parity.md#L87-L89)) already anticipates this: "that route will produce a sibling dict with the wrappers stripped".
+
+   This refines (does not contradict) M5.3's "no transformation" wording. M5.3's `/api/X` will be `jsonify(unwrap_json_strings(view_model_dict))` — a 4-line shim, not real transformation logic.
+
+2. **New package: `internal/web/api/`.** The Go side has no `api/` package today — only [internal/web/server.go](go/internal/web/server.go) with one hello route. The api package owns wire types and (in M5.2) handlers. Sub-files per route keep diffs small.
+
+3. **Wire types are separate from `domain/reconcile.Result`.** [domain/reconcile/reconcile.go:88-92](go/internal/domain/reconcile/reconcile.go#L88-L92) defines `Result`, `MemberResult`, `MonthData`, `TxEntry`, etc. — none have `json:` tags. **Don't tag the domain types**: that bleeds wire concerns into pure logic and locks the JSON contract to internal field names. Define wire types in `internal/web/api/` and convert in M5.2's handlers.
+
+4. **`Expected{Value int; Unknown bool}` with custom `MarshalJSON`/`UnmarshalJSON`** for junior `expected` and `original_expected`. Already prescribed by the master design.
+
+5. **Transaction `amount` / `inferred_amount` may be `int` or `""`** (Sheets `UNFORMATTED_VALUE` returns empty string for blank cells per `scripts/match_payments.py` rows 250-260 in the views.py exploration). Use a custom `SheetsNumber` type with `MarshalJSON`/`UnmarshalJSON` that emits `0`/`null` for empty and the number otherwise. Document in code comment with a one-liner. Verify exact behavior by inspecting one or two existing scrubbed reconcile fixtures before coding.
+
+6. **Schema generation lives in `internal/web/api/schemagen_test.go`** with `-update` flag, à la golden tests. Default test run (`go test ./internal/web/api/...`) re-generates schemas in memory and asserts byte-equality vs the committed files in `tests/fixtures/api-schema/`. `go test -update ./internal/web/api/...` rewrites the committed files. Avoids a separate `cmd/gen-api-schema` binary; CI catches drift automatically.
+
+7. **One schema per route**, named to match the Go type:
+   ```
+   go/tests/fixtures/api-schema/adults.schema.json
+   go/tests/fixtures/api-schema/juniors.schema.json
+   go/tests/fixtures/api-schema/payments.schema.json
+   go/tests/fixtures/api-schema/version.schema.json
+   ```
+
+8. **Adults and Juniors are *not* the same type.** Their outer shapes match (same keys), but `MonthCell.Text` semantics differ (juniors render `"?"`, `"?(3)"`, `:NJ,MA` breakdowns) and `member_data` semantics differ (juniors carry `Expected` sentinel). Define `AdultsResponse` and `JuniorsResponse` separately even if they share most field types — clearer schemas and easier to evolve independently. Share scalar types (`Transaction`, `Exception`, `MonthCell`, `TotalCell`) in `types.go`.
+
+9. **Money is integer CZK** ([master design:55-56](docs/plans/2026-05-03-2349-go-backend-rewrite.md#L55-L56)). All amount fields use `int`. The one exception: `member_data[name].months[YYYY-MM].paid` is a `float64` in the Python output (proportional allocation produces fractional CZK like `33.333333`). Use `float64` only there; document the why in a one-line comment.
+
+## Files to create
+
+```
+go/internal/web/api/
+├── types.go             # SheetsNumber, Expected, Exception, Transaction, MonthCell, TotalCell, MemberRow
+├── adults.go            # AdultsResponse + adults-specific MemberData
+├── juniors.go           # JuniorsResponse + juniors-specific MemberData (with Expected fields)
+├── payments.go          # PaymentsResponse
+├── version.go           # VersionResponse
+└── schemagen_test.go    # generates + golden-asserts schemas
+
+go/tests/fixtures/api-schema/
+├── adults.schema.json
+├── juniors.schema.json
+├── payments.schema.json
+└── version.schema.json
+```
+
+## Struct skeleton (illustrative, not final wording)
+
+```go
+// internal/web/api/types.go
+
+// SheetsNumber wraps a value that may arrive from Google Sheets as either
+// a JSON number or "" (empty string for blank cells). Marshals as 0 when
+// missing; the consumer treats Missing+Value=0 as "no data".
+type SheetsNumber struct {
+    Value   float64
+    Missing bool
+}
+
+// Expected carries a junior's expected fee or the "?" sentinel
+// (single-attendance month requires manual review).
+type Expected struct {
+    Value   int
+    Unknown bool
+}
+
+type Exception struct {
+    Amount int    `json:"amount"`
+    Note   string `json:"note"`
+}
+
+type Transaction struct {
+    Date           string       `json:"date"`
+    Amount         SheetsNumber `json:"amount"`
+    ManualFix      string       `json:"manual_fix"`
+    Person         string       `json:"person"`
+    Purpose        string       `json:"purpose"`
+    InferredAmount SheetsNumber `json:"inferred_amount"`
+    Sender         string       `json:"sender"`
+    Message        string       `json:"message"`
+    BankID         string       `json:"bank_id"`
+}
+
+type MonthCell struct {
+    Text       string `json:"text"`
+    Overridden bool   `json:"overridden"`
+    Status     string `json:"status"` // "empty"|"ok"|"partial"|"unpaid"|"surplus"
+    Amount     int    `json:"amount"`
+    Month      string `json:"month"`      // display label, e.g. "Apr+May 2025"
+    RawMonth   string `json:"raw_month"`  // YYYY-MM
+    Tooltip    string `json:"tooltip"`
+}
+
+type TotalCell struct {
+    Text   string `json:"text"`
+    Status string `json:"status"`
+}
+
+type MemberRow struct {
+    Name              string      `json:"name"`
+    Months            []MonthCell `json:"months"`
+    Balance           int         `json:"balance"`
+    UnpaidPeriods     string      `json:"unpaid_periods"`
+    RawUnpaidPeriods  string      `json:"raw_unpaid_periods"`
+    PayableAmount     int         `json:"payable_amount"`
+}
+
+type Credit struct {
+    Name   string `json:"name"`
+    Amount int    `json:"amount"`
+}
+```
+
+```go
+// internal/web/api/adults.go
+type AdultsMonthData struct {
+    Status      string             `json:"status"`
+    Expected    int                `json:"expected"`
+    Paid        float64            `json:"paid"` // float — proportional allocator can produce 33.333…
+    Exception   *Exception         `json:"exception"`
+    AmountToPay int                `json:"amount_to_pay"`
+    // ... transactions, others, etc — match exact keys from result["members"][name]["months"][YYYY-MM]
+}
+
+type AdultsMemberData struct {
+    TotalBalance int                          `json:"total_balance"`
+    Months       map[string]AdultsMonthData   `json:"months"` // YYYY-MM key
+    Transactions []Transaction                `json:"transactions"`
+}
+
+type AdultsResponse struct {
+    Months          []string                    `json:"months"`
+    RawMonths       []string                    `json:"raw_months"`
+    Results         []MemberRow                 `json:"results"`
+    Totals          []TotalCell                 `json:"totals"`
+    MemberData      map[string]AdultsMemberData `json:"member_data"`
+    MonthLabels     map[string]string           `json:"month_labels"`     // was month_labels_json (string)
+    RawPayments     map[string][]Transaction    `json:"raw_payments"`     // was raw_payments_json (string)
+    Credits         []Credit                    `json:"credits"`
+    Debts           []Credit                    `json:"debts"`
+    Unmatched       []Transaction               `json:"unmatched"`
+    AttendanceURL   string                      `json:"attendance_url"`
+    PaymentsURL     string                      `json:"payments_url"`
+    BankAccount     string                      `json:"bank_account"`
+    CurrentMonth    string                      `json:"current_month"`
+}
+```
+
+`JuniorsResponse` mirrors `AdultsResponse` but the inner `MonthData` carries `Expected` and `OriginalExpected` (both `Expected` type), and adds the `:NJ,MA` breakdown fields produced by [scripts/views.py:290-298](scripts/views.py#L290-L298).
+
+`PaymentsResponse`:
+
+```go
+type PaymentsResponse struct {
+    GroupedPayments map[string][]Transaction `json:"grouped_payments"`
+    SortedPeople    []string                 `json:"sorted_people"`
+    AttendanceURL   string                   `json:"attendance_url"`
+    PaymentsURL     string                   `json:"payments_url"`
+}
+```
+
+`VersionResponse` mirrors Python's `BUILD_META` ([app.py:67](app.py#L67)):
+
+```go
+type VersionResponse struct {
+    Tag       string `json:"tag"`
+    Commit    string `json:"commit"`
+    BuildDate string `json:"build_date"`
+}
+```
+
+Exact fields inside the per-month `MonthData`/`MemberData` will be finalized by inspecting **one** scrubbed `member_data` JSON dump from a current `/adults` and `/juniors` call (see Verification step 1) — names and types have to be identical.
+
+## Reusable existing code
+
+- `domain/reconcile.Result` ([go/internal/domain/reconcile/reconcile.go:88](go/internal/domain/reconcile/reconcile.go#L88)) — source data for adults/juniors. M5.2 maps it to wire types; M5.1 only needs to know the field set.
+- `web.BuildInfo` ([go/internal/web/server.go:11-15](go/internal/web/server.go#L11-L15)) — already wired through `cmd/fuj/main.go:79`. The `VersionResponse` type is a thin renaming of this with json tags. Decide in M5.2 whether to *also* tag `BuildInfo` directly (it's not really domain) or keep `VersionResponse` separate. M5.1 just defines the wire struct.
+- `scripts/views.py` builders — the spec for every key/type. Treat as authoritative.
+
+## Tasks
+
+1. **Add `github.com/invopop/jsonschema` dependency.** `cd go && go get github.com/invopop/jsonschema && go mod tidy`. Single commit.
+2. **Capture one fresh `member_data` dump for adults and juniors** to pin down inner-dict field names and types precisely (especially `paid` precision, `transactions[]` shape, `others[]` if present). Run `make web-py` on a known-good cache, hit `/adults` and `/juniors`, dump `view_model["member_data"]` to a scratch file (gitignored), and inspect. **Do not commit raw dumps** — PII rule. This is for shape inspection only.
+3. **Author `internal/web/api/types.go`** with `SheetsNumber`, `Expected`, `Exception`, `Transaction`, `MonthCell`, `TotalCell`, `MemberRow`, `Credit`. Implement `MarshalJSON`/`UnmarshalJSON` for `SheetsNumber` and `Expected`. Use struct tags `json:"snake_case_key"` matching Python exactly.
+4. **Author `internal/web/api/adults.go`** with `AdultsMonthData`, `AdultsMemberData`, `AdultsResponse`. Cross-check every key against the dump from step 2.
+5. **Author `internal/web/api/juniors.go`** similarly, with `Expected` fields and the J/A breakdown.
+6. **Author `internal/web/api/payments.go` and `version.go`** (small).
+7. **Author `internal/web/api/schemagen_test.go`** that:
+   - Imports `github.com/invopop/jsonschema`.
+   - Defines a `schemaCases` slice: `{name: "adults", typ: AdultsResponse{}, ...}` etc.
+   - For each case, generates a schema, marshals indented JSON, compares against committed file at `../../tests/fixtures/api-schema/<name>.schema.json`.
+   - Honors a `-update` flag (`flag.Bool`) that rewrites the committed file instead of asserting.
+   - One `t.Run(case.name, ...)` per route for clear failure output.
+8. **Run with `-update` once to populate** `tests/fixtures/api-schema/*.schema.json`. Eyeball each schema: required fields list, oneOf for `Expected`, additionalProperties on map types. Commit.
+9. **Lint + test:** `cd go && go vet ./... && make go-test && make go-lint`. Fix any issues. (Expect zero — this is read-only data structures.)
+10. **CHANGELOG entry** + tick `M5.1` in [docs/plans/2026-05-03-2349-go-backend-rewrite-progress.md:100](docs/plans/2026-05-03-2349-go-backend-rewrite-progress.md#L100) with the merge SHA.
+11. **Branch + MR per CLAUDE.md workflow:** branch `feat/go-m5-1-api-structs`, push with `-u`, open MR via `tea pr create`. Do not merge from CLI.
+
+## Verification
+
+1. `cd go && go test ./internal/web/api/...` — **schemas regenerate identically** to committed files.
+2. `cd go && go test ./internal/web/api/... -update` then `git diff go/tests/fixtures/api-schema/` — diff is empty (idempotent generation).
+3. `cd go && make go-lint` — clean.
+4. `cd go && go vet ./...` — clean.
+5. Manual schema inspection: open `adults.schema.json`, confirm:
+   - Top-level `required` list contains every Python key.
+   - `member_data` is `additionalProperties: { ... AdultsMemberData ... }` (a map keyed by name).
+   - `expected` and `original_expected` (juniors only) are `oneOf: [{type: integer}, {const: "?"}]`.
+   - `amount` and `inferred_amount` on `Transaction` accept number or empty/null.
+6. **No production code paths exercised yet** — handlers come in M5.2. Compile-time success + schema golden-test = M5.1 done.
+
+## Out of scope (later M5 tasks)
+
+- Wiring Go HTTP handlers for `/api/X` (M5.2).
+- Adding Python `/api/X` shadow endpoints (M5.3) — including the `unwrap_json_strings(view_model)` shim noted in design decision #1.
+- `cmd/parity/main.go` and `make parity` target (M5.4).
+- Tagging `domain/reconcile.Result` with `json:` tags — explicitly avoided.
+- Refactoring the strings-of-JSON fields out of the Python view-model — they stay in `views.py` for the template path, the `/api/X` shadow unwraps them.
diff --git a/go/go.mod b/go/go.mod
index 1cb254e..ccc4b54 100644
--- a/go/go.mod
+++ b/go/go.mod
@@ -3,6 +3,7 @@ module fuj-management/go
 go 1.26.1
 
 require (
+	github.com/invopop/jsonschema v0.14.0
 	golang.org/x/net v0.53.0
 	golang.org/x/text v0.36.0
 	google.golang.org/api v0.278.0
@@ -12,6 +13,8 @@ require (
 	cloud.google.com/go/auth v0.20.0 // indirect
 	cloud.google.com/go/auth/oauth2adapt v0.2.8 // indirect
 	cloud.google.com/go/compute/metadata v0.9.0 // indirect
+	github.com/bahlo/generic-list-go v0.2.0 // indirect
+	github.com/buger/jsonparser v1.1.2 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/felixge/httpsnoop v1.0.4 // indirect
 	github.com/go-logr/logr v1.4.3 // indirect
@@ -20,11 +23,13 @@ require (
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/googleapis/enterprise-certificate-proxy v0.3.15 // indirect
 	github.com/googleapis/gax-go/v2 v2.22.0 // indirect
+	github.com/pb33f/ordered-map/v2 v2.3.1 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.67.0 // indirect
 	go.opentelemetry.io/otel v1.43.0 // indirect
 	go.opentelemetry.io/otel/metric v1.43.0 // indirect
 	go.opentelemetry.io/otel/trace v1.43.0 // indirect
+	go.yaml.in/yaml/v4 v4.0.0-rc.2 // indirect
 	golang.org/x/crypto v0.50.0 // indirect
 	golang.org/x/oauth2 v0.36.0 // indirect
 	golang.org/x/sys v0.43.0 // indirect
diff --git a/go/go.sum b/go/go.sum
index 11193b0..b975380 100644
--- a/go/go.sum
+++ b/go/go.sum
@@ -4,6 +4,10 @@ cloud.google.com/go/auth/oauth2adapt v0.2.8 h1:keo8NaayQZ6wimpNSmW5OPc283g65QNIi
 cloud.google.com/go/auth/oauth2adapt v0.2.8/go.mod h1:XQ9y31RkqZCcwJWNSx2Xvric3RrU88hAYYbjDWYDL+c=
 cloud.google.com/go/compute/metadata v0.9.0 h1:pDUj4QMoPejqq20dK0Pg2N4yG9zIkYGdBtwLoEkH9Zs=
 cloud.google.com/go/compute/metadata v0.9.0/go.mod h1:E0bWwX5wTnLPedCKqk3pJmVgCBSM6qQI1yTBdEb3C10=
+github.com/bahlo/generic-list-go v0.2.0 h1:5sz/EEAK+ls5wF+NeqDpk5+iNdMDXrh3z3nPnH1Wvgk=
+github.com/bahlo/generic-list-go v0.2.0/go.mod h1:2KvAjgMlE5NNynlg/5iLrrCCZ2+5xWbdbCW3pNTGyYg=
+github.com/buger/jsonparser v1.1.2 h1:frqHqw7otoVbk5M8LlE/L7HTnIq2v9RX6EJ48i9AxJk=
+github.com/buger/jsonparser v1.1.2/go.mod h1:6RYKKt7H4d4+iWqouImQ9R2FZql3VbhNgx27UK13J/0=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
 github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
@@ -27,6 +31,10 @@ github.com/googleapis/enterprise-certificate-proxy v0.3.15 h1:xolVQTEXusUcAA5Ugt
 github.com/googleapis/enterprise-certificate-proxy v0.3.15/go.mod h1:vqVt9yG9480NtzREnTlmGSBmFrA+bzb0yl0TxoBQXOg=
 github.com/googleapis/gax-go/v2 v2.22.0 h1:PjIWBpgGIVKGoCXuiCoP64altEJCj3/Ei+kSU5vlZD4=
 github.com/googleapis/gax-go/v2 v2.22.0/go.mod h1:irWBbALSr0Sk3qlqb9SyJ1h68WjgeFuiOzI4Rqw5+aY=
+github.com/invopop/jsonschema v0.14.0 h1:MHQqLhvpNUZfw+hM3AZDYK7jxO8FZoQeQM77g8iyZjg=
+github.com/invopop/jsonschema v0.14.0/go.mod h1:ygm6C2EaVNMBDPpaPlnOA2pFAxBnxGjFlMZABxm9n2I=
+github.com/pb33f/ordered-map/v2 v2.3.1 h1:5319HDO0aw4DA4gzi+zv4FXU9UlSs3xGZ40wcP1nBjY=
+github.com/pb33f/ordered-map/v2 v2.3.1/go.mod h1:qxFQgd0PkVUtOMCkTapqotNgzRhMPL7VvaHKbd1HnmQ=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
@@ -45,6 +53,8 @@ go.opentelemetry.io/otel/sdk/metric v1.43.0 h1:S88dyqXjJkuBNLeMcVPRFXpRw2fuwdvfC
 go.opentelemetry.io/otel/sdk/metric v1.43.0/go.mod h1:C/RJtwSEJ5hzTiUz5pXF1kILHStzb9zFlIEe85bhj6A=
 go.opentelemetry.io/otel/trace v1.43.0 h1:BkNrHpup+4k4w+ZZ86CZoHHEkohws8AY+WTX09nk+3A=
 go.opentelemetry.io/otel/trace v1.43.0/go.mod h1:/QJhyVBUUswCphDVxq+8mld+AvhXZLhe+8WVFxiFff0=
+go.yaml.in/yaml/v4 v4.0.0-rc.2 h1:/FrI8D64VSr4HtGIlUtlFMGsm7H7pWTbj6vOLVZcA6s=
+go.yaml.in/yaml/v4 v4.0.0-rc.2/go.mod h1:aZqd9kCMsGL7AuUv/m/PvWLdg5sjJsZ4oHDEnfPPfY0=
 golang.org/x/crypto v0.50.0 h1:zO47/JPrL6vsNkINmLoo/PH1gcxpls50DNogFvB5ZGI=
 golang.org/x/crypto v0.50.0/go.mod h1:3muZ7vA7PBCE6xgPX7nkzzjiUq87kRItoJQM1Yo8S+Q=
 golang.org/x/net v0.53.0 h1:d+qAbo5L0orcWAr0a9JweQpjXF19LMXJE8Ey7hwOdUA=
diff --git a/go/internal/web/api/adults.go b/go/internal/web/api/adults.go
new file mode 100644
index 0000000..f891e3a
--- /dev/null
+++ b/go/internal/web/api/adults.go
@@ -0,0 +1,42 @@
+package api
+
+// AdultsMonthData is the reconciled ledger for one adult member in one month.
+// Keys match Python's result["members"][name]["months"][YYYY-MM].
+type AdultsMonthData struct {
+	Expected         int             `json:"expected"`
+	OriginalExpected int             `json:"original_expected"`
+	AttendanceCount  int             `json:"attendance_count"`
+	Exception        *ExceptionData  `json:"exception"`
+	Paid             float64         `json:"paid"` // float: proportional allocator may produce fractional CZK
+	Transactions     []MemberTxEntry `json:"transactions"`
+}
+
+// AdultsMemberData is the reconciled ledger for one adult member.
+// Keys match Python's result["members"][name].
+type AdultsMemberData struct {
+	Tier              string                     `json:"tier"`
+	Months            map[string]AdultsMonthData `json:"months"` // YYYY-MM → month data
+	OtherTransactions []MemberOtherEntry         `json:"other_transactions"`
+	TotalBalance      int                        `json:"total_balance"`
+}
+
+// AdultsResponse is the JSON contract for GET /api/adults.
+// MemberData, MonthLabels, and RawPayments correspond to the Python view-model
+// fields member_data, month_labels_json, and raw_payments_json respectively,
+// but as nested objects rather than pre-serialised JSON strings.
+type AdultsResponse struct {
+	Months        []string                    `json:"months"`     // display labels
+	RawMonths     []string                    `json:"raw_months"` // "YYYY-MM"
+	Results       []MemberRow                 `json:"results"`
+	Totals        []TotalCell                 `json:"totals"`
+	MemberData    map[string]AdultsMemberData `json:"member_data"`  // name → ledger
+	MonthLabels   map[string]string           `json:"month_labels"` // YYYY-MM → display label
+	RawPayments   map[string][]RawTransaction `json:"raw_payments"` // name → raw sheet rows
+	Credits       []Credit                    `json:"credits"`
+	Debts         []Credit                    `json:"debts"`
+	Unmatched     []RawTransaction            `json:"unmatched"`
+	AttendanceURL string                      `json:"attendance_url"`
+	PaymentsURL   string                      `json:"payments_url"`
+	BankAccount   string                      `json:"bank_account"`
+	CurrentMonth  string                      `json:"current_month"`
+}
diff --git a/go/internal/web/api/juniors.go b/go/internal/web/api/juniors.go
new file mode 100644
index 0000000..d07c777
--- /dev/null
+++ b/go/internal/web/api/juniors.go
@@ -0,0 +1,41 @@
+package api
+
+// JuniorsMonthData is the reconciled ledger for one junior member in one month.
+// expected and original_expected may be the "?" sentinel (single-attendance month
+// requiring manual review); they are carried via the Expected type.
+type JuniorsMonthData struct {
+	Expected         Expected        `json:"expected"`
+	OriginalExpected Expected        `json:"original_expected"`
+	AttendanceCount  int             `json:"attendance_count"`
+	Exception        *ExceptionData  `json:"exception"`
+	Paid             float64         `json:"paid"`
+	Transactions     []MemberTxEntry `json:"transactions"`
+}
+
+// JuniorsMemberData is the reconciled ledger for one junior member.
+type JuniorsMemberData struct {
+	Tier              string                      `json:"tier"`
+	Months            map[string]JuniorsMonthData `json:"months"`
+	OtherTransactions []MemberOtherEntry          `json:"other_transactions"`
+	TotalBalance      int                         `json:"total_balance"`
+}
+
+// JuniorsResponse is the JSON contract for GET /api/juniors.
+// Same outer shape as AdultsResponse; differs in that member_data carries
+// Expected (int or "?") for expected/original_expected fields.
+type JuniorsResponse struct {
+	Months        []string                     `json:"months"`
+	RawMonths     []string                     `json:"raw_months"`
+	Results       []MemberRow                  `json:"results"`
+	Totals        []TotalCell                  `json:"totals"`
+	MemberData    map[string]JuniorsMemberData `json:"member_data"`
+	MonthLabels   map[string]string            `json:"month_labels"`
+	RawPayments   map[string][]RawTransaction  `json:"raw_payments"`
+	Credits       []Credit                     `json:"credits"`
+	Debts         []Credit                     `json:"debts"`
+	Unmatched     []RawTransaction             `json:"unmatched"`
+	AttendanceURL string                       `json:"attendance_url"`
+	PaymentsURL   string                       `json:"payments_url"`
+	BankAccount   string                       `json:"bank_account"`
+	CurrentMonth  string                       `json:"current_month"`
+}
diff --git a/go/internal/web/api/payments.go b/go/internal/web/api/payments.go
new file mode 100644
index 0000000..01a47d4
--- /dev/null
+++ b/go/internal/web/api/payments.go
@@ -0,0 +1,9 @@
+package api
+
+// PaymentsResponse is the JSON contract for GET /api/payments.
+type PaymentsResponse struct {
+	GroupedPayments map[string][]RawTransaction `json:"grouped_payments"` // person name → rows
+	SortedPeople    []string                    `json:"sorted_people"`
+	AttendanceURL   string                      `json:"attendance_url"`
+	PaymentsURL     string                      `json:"payments_url"`
+}
diff --git a/go/internal/web/api/schemagen_test.go b/go/internal/web/api/schemagen_test.go
new file mode 100644
index 0000000..7b277a2
--- /dev/null
+++ b/go/internal/web/api/schemagen_test.go
@@ -0,0 +1,81 @@
+package api
+
+// schemagen_test.go generates and golden-compares JSON Schema files for every
+// /api/X response type.
+//
+// Normal run (CI): go test ./internal/web/api/... — asserts schemas match committed files.
+// Regenerate:      go test -run TestGenerateSchemas -update ./internal/web/api/...
+
+import (
+	"encoding/json"
+	"flag"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/invopop/jsonschema"
+)
+
+var updateFlag = flag.Bool("update", false, "overwrite api-schema fixture files with freshly generated schemas")
+
+// JSONSchema makes Expected self-describing for the reflector at test time.
+// The method is in a test file and is not compiled into production binaries.
+// It emits oneOf [integer, "?"] to match the custom MarshalJSON behaviour.
+func (Expected) JSONSchema() *jsonschema.Schema {
+	return &jsonschema.Schema{
+		OneOf: []*jsonschema.Schema{
+			{Type: "integer"},
+			{Enum: []any{"?"}},
+		},
+	}
+}
+
+func TestGenerateSchemas(t *testing.T) {
+	r := &jsonschema.Reflector{
+		AllowAdditionalProperties: false,
+	}
+
+	cases := []struct {
+		name string
+		val  any
+	}{
+		{"adults", &AdultsResponse{}},
+		{"juniors", &JuniorsResponse{}},
+		{"payments", &PaymentsResponse{}},
+		{"version", &VersionResponse{}},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			schema := r.Reflect(tc.val)
+
+			got, err := json.MarshalIndent(schema, "", "  ")
+			if err != nil {
+				t.Fatalf("marshal schema: %v", err)
+			}
+			got = append(got, '\n')
+
+			// Path: go/internal/web/api/ → ../../.. → go/ → tests/fixtures/api-schema/
+			path := filepath.Join("..", "..", "..", "tests", "fixtures", "api-schema", tc.name+".schema.json")
+
+			if *updateFlag {
+				if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+					t.Fatalf("mkdir: %v", err)
+				}
+				if err := os.WriteFile(path, got, 0o644); err != nil {
+					t.Fatalf("write schema: %v", err)
+				}
+				t.Logf("wrote %s", path)
+				return
+			}
+
+			want, err := os.ReadFile(path)
+			if err != nil {
+				t.Fatalf("read fixture %s: %v (re-run with -update to generate)", path, err)
+			}
+			if string(got) != string(want) {
+				t.Errorf("schema mismatch for %s; re-run with -update to regenerate", tc.name)
+			}
+		})
+	}
+}
diff --git a/go/internal/web/api/types.go b/go/internal/web/api/types.go
new file mode 100644
index 0000000..9e97abf
--- /dev/null
+++ b/go/internal/web/api/types.go
@@ -0,0 +1,122 @@
+// Package api defines wire types for the JSON API contract (/api/...).
+// These structs have explicit json: tags matching the Python view-model dict
+// keys so that M5 parity tests can do byte-equal comparison between backends.
+//
+// The three Python template-only JSON-string fields (member_data,
+// month_labels_json, raw_payments_json) are represented here as nested objects;
+// the Python /api/X shadow endpoint strips the json.dumps wrappers before
+// serialising.
+package api
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// Expected holds a junior fee expectation: either a concrete integer or the
+// "?" sentinel (single-attendance month requiring manual review).
+// MarshalJSON emits the integer or the JSON string "?".
+type Expected struct {
+	Value   int
+	Unknown bool
+}
+
+func (e Expected) MarshalJSON() ([]byte, error) {
+	if e.Unknown {
+		return []byte(`"?"`), nil
+	}
+	return json.Marshal(e.Value)
+}
+
+func (e *Expected) UnmarshalJSON(data []byte) error {
+	if len(data) > 0 && data[0] == '"' {
+		var s string
+		if err := json.Unmarshal(data, &s); err != nil {
+			return err
+		}
+		if s == "?" {
+			e.Unknown = true
+			return nil
+		}
+		return fmt.Errorf("api.Expected: unexpected string %q", s)
+	}
+	e.Unknown = false
+	return json.Unmarshal(data, &e.Value)
+}
+
+// ExceptionData is a manual fee override for one member in one month.
+type ExceptionData struct {
+	Amount int    `json:"amount"`
+	Note   string `json:"note"`
+}
+
+// MemberTxEntry is one payment allocation to a member+month, as stored in
+// member_data.months[YYYY-MM].transactions.
+type MemberTxEntry struct {
+	Amount     float64 `json:"amount"`
+	Date       string  `json:"date"`
+	Sender     string  `json:"sender"`
+	Message    string  `json:"message"`
+	Confidence string  `json:"confidence"`
+}
+
+// MemberOtherEntry is an "other:…" purpose payment allocated to a member.
+type MemberOtherEntry struct {
+	Amount     float64 `json:"amount"`
+	Date       string  `json:"date"`
+	Sender     string  `json:"sender"`
+	Message    string  `json:"message"`
+	Purpose    string  `json:"purpose"`
+	Confidence string  `json:"confidence"`
+}
+
+// RawTransaction is a full payments-sheet row.
+// Used for unmatched transactions and raw_payments groupings.
+// Columns match the sheet layout: Date|Amount|manual fix|Person|Purpose|
+// Inferred Amount|Sender|VS|Message|Bank ID|Sync ID.
+type RawTransaction struct {
+	Date           string  `json:"date"`
+	Amount         float64 `json:"amount"`
+	ManualFix      string  `json:"manual_fix"`
+	Person         string  `json:"person"`
+	Purpose        string  `json:"purpose"`
+	InferredAmount float64 `json:"inferred_amount"`
+	Sender         string  `json:"sender"`
+	VS             string  `json:"vs"`
+	Message        string  `json:"message"`
+	BankID         string  `json:"bank_id"`
+	SyncID         string  `json:"sync_id"`
+}
+
+// MonthCell is one cell in a member's month column on the dashboard.
+type MonthCell struct {
+	Text       string `json:"text"`
+	Overridden bool   `json:"overridden"`
+	Status     string `json:"status"` // "empty"|"ok"|"partial"|"unpaid"|"surplus"
+	Amount     int    `json:"amount"`
+	Month      string `json:"month"`     // display label, e.g. "Apr+May 2025"
+	RawMonth   string `json:"raw_month"` // "YYYY-MM"
+	Tooltip    string `json:"tooltip"`
+}
+
+// TotalCell is one cell in the monthly totals row.
+type TotalCell struct {
+	Text   string `json:"text"`
+	Status string `json:"status"`
+}
+
+// MemberRow is one member's summary row in the dashboard results table.
+type MemberRow struct {
+	Name             string      `json:"name"`
+	Months           []MonthCell `json:"months"`
+	Balance          int         `json:"balance"`
+	UnpaidPeriods    string      `json:"unpaid_periods"`
+	RawUnpaidPeriods string      `json:"raw_unpaid_periods"`
+	PayableAmount    int         `json:"payable_amount"`
+}
+
+// Credit is one entry in the credits or debts lists.
+type Credit struct {
+	Name   string `json:"name"`
+	Amount int    `json:"amount"`
+}
diff --git a/go/internal/web/api/version.go b/go/internal/web/api/version.go
new file mode 100644
index 0000000..21593a6
--- /dev/null
+++ b/go/internal/web/api/version.go
@@ -0,0 +1,9 @@
+package api
+
+// VersionResponse is the JSON contract for GET /api/version.
+// Keys match Python's BUILD_META dict (see app.py).
+type VersionResponse struct {
+	Tag       string `json:"tag"`
+	Commit    string `json:"commit"`
+	BuildDate string `json:"build_date"`
+}
diff --git a/go/tests/fixtures/api-schema/adults.schema.json b/go/tests/fixtures/api-schema/adults.schema.json
new file mode 100644
index 0000000..437b227
--- /dev/null
+++ b/go/tests/fixtures/api-schema/adults.schema.json
@@ -0,0 +1,399 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$ref": "#/$defs/AdultsResponse",
+  "$defs": {
+    "AdultsMemberData": {
+      "properties": {
+        "tier": {
+          "type": "string"
+        },
+        "months": {
+          "additionalProperties": {
+            "$ref": "#/$defs/AdultsMonthData"
+          },
+          "type": "object"
+        },
+        "other_transactions": {
+          "items": {
+            "$ref": "#/$defs/MemberOtherEntry"
+          },
+          "type": "array"
+        },
+        "total_balance": {
+          "type": "integer"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "tier",
+        "months",
+        "other_transactions",
+        "total_balance"
+      ]
+    },
+    "AdultsMonthData": {
+      "properties": {
+        "expected": {
+          "type": "integer"
+        },
+        "original_expected": {
+          "type": "integer"
+        },
+        "attendance_count": {
+          "type": "integer"
+        },
+        "exception": {
+          "$ref": "#/$defs/ExceptionData"
+        },
+        "paid": {
+          "type": "number"
+        },
+        "transactions": {
+          "items": {
+            "$ref": "#/$defs/MemberTxEntry"
+          },
+          "type": "array"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "expected",
+        "original_expected",
+        "attendance_count",
+        "exception",
+        "paid",
+        "transactions"
+      ]
+    },
+    "AdultsResponse": {
+      "properties": {
+        "months": {
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        },
+        "raw_months": {
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        },
+        "results": {
+          "items": {
+            "$ref": "#/$defs/MemberRow"
+          },
+          "type": "array"
+        },
+        "totals": {
+          "items": {
+            "$ref": "#/$defs/TotalCell"
+          },
+          "type": "array"
+        },
+        "member_data": {
+          "additionalProperties": {
+            "$ref": "#/$defs/AdultsMemberData"
+          },
+          "type": "object"
+        },
+        "month_labels": {
+          "additionalProperties": {
+            "type": "string"
+          },
+          "type": "object"
+        },
+        "raw_payments": {
+          "additionalProperties": {
+            "items": {
+              "$ref": "#/$defs/RawTransaction"
+            },
+            "type": "array"
+          },
+          "type": "object"
+        },
+        "credits": {
+          "items": {
+            "$ref": "#/$defs/Credit"
+          },
+          "type": "array"
+        },
+        "debts": {
+          "items": {
+            "$ref": "#/$defs/Credit"
+          },
+          "type": "array"
+        },
+        "unmatched": {
+          "items": {
+            "$ref": "#/$defs/RawTransaction"
+          },
+          "type": "array"
+        },
+        "attendance_url": {
+          "type": "string"
+        },
+        "payments_url": {
+          "type": "string"
+        },
+        "bank_account": {
+          "type": "string"
+        },
+        "current_month": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "months",
+        "raw_months",
+        "results",
+        "totals",
+        "member_data",
+        "month_labels",
+        "raw_payments",
+        "credits",
+        "debts",
+        "unmatched",
+        "attendance_url",
+        "payments_url",
+        "bank_account",
+        "current_month"
+      ]
+    },
+    "Credit": {
+      "properties": {
+        "name": {
+          "type": "string"
+        },
+        "amount": {
+          "type": "integer"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "name",
+        "amount"
+      ]
+    },
+    "ExceptionData": {
+      "properties": {
+        "amount": {
+          "type": "integer"
+        },
+        "note": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "amount",
+        "note"
+      ]
+    },
+    "MemberOtherEntry": {
+      "properties": {
+        "amount": {
+          "type": "number"
+        },
+        "date": {
+          "type": "string"
+        },
+        "sender": {
+          "type": "string"
+        },
+        "message": {
+          "type": "string"
+        },
+        "purpose": {
+          "type": "string"
+        },
+        "confidence": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "amount",
+        "date",
+        "sender",
+        "message",
+        "purpose",
+        "confidence"
+      ]
+    },
+    "MemberRow": {
+      "properties": {
+        "name": {
+          "type": "string"
+        },
+        "months": {
+          "items": {
+            "$ref": "#/$defs/MonthCell"
+          },
+          "type": "array"
+        },
+        "balance": {
+          "type": "integer"
+        },
+        "unpaid_periods": {
+          "type": "string"
+        },
+        "raw_unpaid_periods": {
+          "type": "string"
+        },
+        "payable_amount": {
+          "type": "integer"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "name",
+        "months",
+        "balance",
+        "unpaid_periods",
+        "raw_unpaid_periods",
+        "payable_amount"
+      ]
+    },
+    "MemberTxEntry": {
+      "properties": {
+        "amount": {
+          "type": "number"
+        },
+        "date": {
+          "type": "string"
+        },
+        "sender": {
+          "type": "string"
+        },
+        "message": {
+          "type": "string"
+        },
+        "confidence": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "amount",
+        "date",
+        "sender",
+        "message",
+        "confidence"
+      ]
+    },
+    "MonthCell": {
+      "properties": {
+        "text": {
+          "type": "string"
+        },
+        "overridden": {
+          "type": "boolean"
+        },
+        "status": {
+          "type": "string"
+        },
+        "amount": {
+          "type": "integer"
+        },
+        "month": {
+          "type": "string"
+        },
+        "raw_month": {
+          "type": "string"
+        },
+        "tooltip": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "text",
+        "overridden",
+        "status",
+        "amount",
+        "month",
+        "raw_month",
+        "tooltip"
+      ]
+    },
+    "RawTransaction": {
+      "properties": {
+        "date": {
+          "type": "string"
+        },
+        "amount": {
+          "type": "number"
+        },
+        "manual_fix": {
+          "type": "string"
+        },
+        "person": {
+          "type": "string"
+        },
+        "purpose": {
+          "type": "string"
+        },
+        "inferred_amount": {
+          "type": "number"
+        },
+        "sender": {
+          "type": "string"
+        },
+        "vs": {
+          "type": "string"
+        },
+        "message": {
+          "type": "string"
+        },
+        "bank_id": {
+          "type": "string"
+        },
+        "sync_id": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "date",
+        "amount",
+        "manual_fix",
+        "person",
+        "purpose",
+        "inferred_amount",
+        "sender",
+        "vs",
+        "message",
+        "bank_id",
+        "sync_id"
+      ]
+    },
+    "TotalCell": {
+      "properties": {
+        "text": {
+          "type": "string"
+        },
+        "status": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "text",
+        "status"
+      ]
+    }
+  }
+}
diff --git a/go/tests/fixtures/api-schema/juniors.schema.json b/go/tests/fixtures/api-schema/juniors.schema.json
new file mode 100644
index 0000000..337a62e
--- /dev/null
+++ b/go/tests/fixtures/api-schema/juniors.schema.json
@@ -0,0 +1,411 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$ref": "#/$defs/JuniorsResponse",
+  "$defs": {
+    "Credit": {
+      "properties": {
+        "name": {
+          "type": "string"
+        },
+        "amount": {
+          "type": "integer"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "name",
+        "amount"
+      ]
+    },
+    "ExceptionData": {
+      "properties": {
+        "amount": {
+          "type": "integer"
+        },
+        "note": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "amount",
+        "note"
+      ]
+    },
+    "Expected": {
+      "oneOf": [
+        {
+          "type": "integer"
+        },
+        {
+          "enum": [
+            "?"
+          ]
+        }
+      ]
+    },
+    "JuniorsMemberData": {
+      "properties": {
+        "tier": {
+          "type": "string"
+        },
+        "months": {
+          "additionalProperties": {
+            "$ref": "#/$defs/JuniorsMonthData"
+          },
+          "type": "object"
+        },
+        "other_transactions": {
+          "items": {
+            "$ref": "#/$defs/MemberOtherEntry"
+          },
+          "type": "array"
+        },
+        "total_balance": {
+          "type": "integer"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "tier",
+        "months",
+        "other_transactions",
+        "total_balance"
+      ]
+    },
+    "JuniorsMonthData": {
+      "properties": {
+        "expected": {
+          "$ref": "#/$defs/Expected"
+        },
+        "original_expected": {
+          "$ref": "#/$defs/Expected"
+        },
+        "attendance_count": {
+          "type": "integer"
+        },
+        "exception": {
+          "$ref": "#/$defs/ExceptionData"
+        },
+        "paid": {
+          "type": "number"
+        },
+        "transactions": {
+          "items": {
+            "$ref": "#/$defs/MemberTxEntry"
+          },
+          "type": "array"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "expected",
+        "original_expected",
+        "attendance_count",
+        "exception",
+        "paid",
+        "transactions"
+      ]
+    },
+    "JuniorsResponse": {
+      "properties": {
+        "months": {
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        },
+        "raw_months": {
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        },
+        "results": {
+          "items": {
+            "$ref": "#/$defs/MemberRow"
+          },
+          "type": "array"
+        },
+        "totals": {
+          "items": {
+            "$ref": "#/$defs/TotalCell"
+          },
+          "type": "array"
+        },
+        "member_data": {
+          "additionalProperties": {
+            "$ref": "#/$defs/JuniorsMemberData"
+          },
+          "type": "object"
+        },
+        "month_labels": {
+          "additionalProperties": {
+            "type": "string"
+          },
+          "type": "object"
+        },
+        "raw_payments": {
+          "additionalProperties": {
+            "items": {
+              "$ref": "#/$defs/RawTransaction"
+            },
+            "type": "array"
+          },
+          "type": "object"
+        },
+        "credits": {
+          "items": {
+            "$ref": "#/$defs/Credit"
+          },
+          "type": "array"
+        },
+        "debts": {
+          "items": {
+            "$ref": "#/$defs/Credit"
+          },
+          "type": "array"
+        },
+        "unmatched": {
+          "items": {
+            "$ref": "#/$defs/RawTransaction"
+          },
+          "type": "array"
+        },
+        "attendance_url": {
+          "type": "string"
+        },
+        "payments_url": {
+          "type": "string"
+        },
+        "bank_account": {
+          "type": "string"
+        },
+        "current_month": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "months",
+        "raw_months",
+        "results",
+        "totals",
+        "member_data",
+        "month_labels",
+        "raw_payments",
+        "credits",
+        "debts",
+        "unmatched",
+        "attendance_url",
+        "payments_url",
+        "bank_account",
+        "current_month"
+      ]
+    },
+    "MemberOtherEntry": {
+      "properties": {
+        "amount": {
+          "type": "number"
+        },
+        "date": {
+          "type": "string"
+        },
+        "sender": {
+          "type": "string"
+        },
+        "message": {
+          "type": "string"
+        },
+        "purpose": {
+          "type": "string"
+        },
+        "confidence": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "amount",
+        "date",
+        "sender",
+        "message",
+        "purpose",
+        "confidence"
+      ]
+    },
+    "MemberRow": {
+      "properties": {
+        "name": {
+          "type": "string"
+        },
+        "months": {
+          "items": {
+            "$ref": "#/$defs/MonthCell"
+          },
+          "type": "array"
+        },
+        "balance": {
+          "type": "integer"
+        },
+        "unpaid_periods": {
+          "type": "string"
+        },
+        "raw_unpaid_periods": {
+          "type": "string"
+        },
+        "payable_amount": {
+          "type": "integer"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "name",
+        "months",
+        "balance",
+        "unpaid_periods",
+        "raw_unpaid_periods",
+        "payable_amount"
+      ]
+    },
+    "MemberTxEntry": {
+      "properties": {
+        "amount": {
+          "type": "number"
+        },
+        "date": {
+          "type": "string"
+        },
+        "sender": {
+          "type": "string"
+        },
+        "message": {
+          "type": "string"
+        },
+        "confidence": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "amount",
+        "date",
+        "sender",
+        "message",
+        "confidence"
+      ]
+    },
+    "MonthCell": {
+      "properties": {
+        "text": {
+          "type": "string"
+        },
+        "overridden": {
+          "type": "boolean"
+        },
+        "status": {
+          "type": "string"
+        },
+        "amount": {
+          "type": "integer"
+        },
+        "month": {
+          "type": "string"
+        },
+        "raw_month": {
+          "type": "string"
+        },
+        "tooltip": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "text",
+        "overridden",
+        "status",
+        "amount",
+        "month",
+        "raw_month",
+        "tooltip"
+      ]
+    },
+    "RawTransaction": {
+      "properties": {
+        "date": {
+          "type": "string"
+        },
+        "amount": {
+          "type": "number"
+        },
+        "manual_fix": {
+          "type": "string"
+        },
+        "person": {
+          "type": "string"
+        },
+        "purpose": {
+          "type": "string"
+        },
+        "inferred_amount": {
+          "type": "number"
+        },
+        "sender": {
+          "type": "string"
+        },
+        "vs": {
+          "type": "string"
+        },
+        "message": {
+          "type": "string"
+        },
+        "bank_id": {
+          "type": "string"
+        },
+        "sync_id": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "date",
+        "amount",
+        "manual_fix",
+        "person",
+        "purpose",
+        "inferred_amount",
+        "sender",
+        "vs",
+        "message",
+        "bank_id",
+        "sync_id"
+      ]
+    },
+    "TotalCell": {
+      "properties": {
+        "text": {
+          "type": "string"
+        },
+        "status": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "text",
+        "status"
+      ]
+    }
+  }
+}
diff --git a/go/tests/fixtures/api-schema/payments.schema.json b/go/tests/fixtures/api-schema/payments.schema.json
new file mode 100644
index 0000000..8993c3b
--- /dev/null
+++ b/go/tests/fixtures/api-schema/payments.schema.json
@@ -0,0 +1,91 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$ref": "#/$defs/PaymentsResponse",
+  "$defs": {
+    "PaymentsResponse": {
+      "properties": {
+        "grouped_payments": {
+          "additionalProperties": {
+            "items": {
+              "$ref": "#/$defs/RawTransaction"
+            },
+            "type": "array"
+          },
+          "type": "object"
+        },
+        "sorted_people": {
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        },
+        "attendance_url": {
+          "type": "string"
+        },
+        "payments_url": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "grouped_payments",
+        "sorted_people",
+        "attendance_url",
+        "payments_url"
+      ]
+    },
+    "RawTransaction": {
+      "properties": {
+        "date": {
+          "type": "string"
+        },
+        "amount": {
+          "type": "number"
+        },
+        "manual_fix": {
+          "type": "string"
+        },
+        "person": {
+          "type": "string"
+        },
+        "purpose": {
+          "type": "string"
+        },
+        "inferred_amount": {
+          "type": "number"
+        },
+        "sender": {
+          "type": "string"
+        },
+        "vs": {
+          "type": "string"
+        },
+        "message": {
+          "type": "string"
+        },
+        "bank_id": {
+          "type": "string"
+        },
+        "sync_id": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "date",
+        "amount",
+        "manual_fix",
+        "person",
+        "purpose",
+        "inferred_amount",
+        "sender",
+        "vs",
+        "message",
+        "bank_id",
+        "sync_id"
+      ]
+    }
+  }
+}
diff --git a/go/tests/fixtures/api-schema/version.schema.json b/go/tests/fixtures/api-schema/version.schema.json
new file mode 100644
index 0000000..0736a7a
--- /dev/null
+++ b/go/tests/fixtures/api-schema/version.schema.json
@@ -0,0 +1,26 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$ref": "#/$defs/VersionResponse",
+  "$defs": {
+    "VersionResponse": {
+      "properties": {
+        "tag": {
+          "type": "string"
+        },
+        "commit": {
+          "type": "string"
+        },
+        "build_date": {
+          "type": "string"
+        }
+      },
+      "additionalProperties": false,
+      "type": "object",
+      "required": [
+        "tag",
+        "commit",
+        "build_date"
+      ]
+    }
+  }
+}