> ## Documentation Index > Fetch the complete documentation index at: https://docs.pay.aptahq.com/llms.txt > Use this file to discover all available pages before exploring further. # OTP / PIN / 3DS step > **Finish a charge that came back `requires_action`.** When a collection needs a second step from the customer — an SMS OTP, a momo PIN, a 3-D Secure result — you collect that value in your UI and submit it here against the transaction's gateway reference. Returns the updated transaction. The status may still be `pending` afterwards: authorizing proves the customer consented, it does not prove the provider has settled, so keep watching the webhook or poll `GET /v1/collections/{reference}`. **This call validates the code AND charges.** With the upstream provider there is no separate "authorize" step — authorizing re-sends the charge with the code attached, so a correct code debits the customer immediately: they get the handset PIN prompt (STK push), and success or failure arrives by webhook. Expect `pending` here and treat the webhook as the answer. `pin_id` comes from the `next_action` on the charge (or from `POST /v1/collections/otp` if you drove that yourself); `pin` is what the customer typed. A wrong code fails this call without failing the transaction — prompt again and retry. **`source` must be resupplied.** Re-sending the charge needs the payer's full number, and the gateway never stores one — only its last 4 digits (so a leaked database cannot become a list of customer phone numbers). The `last4` of what you send is checked against the transaction, so a reference cannot be redirected to a different payer. The amount, currency and country come from the stored transaction and cannot be changed here. ## OpenAPI ````yaml /openapi.json post /v1/collections/{reference}/authorize openapi: 3.0.3 info: title: AptaPay Gateway version: 1.0.0 description: > One provider-neutral payment API owned by many apps: collections, payouts, bank resolution and FX, with signed webhooks back. ## Authentication Every `/v1/*` request carries four headers. **A plain API key is not enough** — a key in a proxy log or an error report would be immediately usable, whereas a signature binds the request to a body and a moment. | Header | Value | | --- | --- | | `X-AptaPay-Key` | `{app_id}.{key_id}.{api_key}` | | `X-AptaPay-Timestamp` | unix seconds | | `X-AptaPay-Nonce` | 16-64 chars, `[A-Za-z0-9_-]`, unique per request | | `X-AptaPay-Signature` | `v1={hex HMAC-SHA256}` | The signature is HMAC-SHA256, with your **inbound** signing secret, over exactly these ten fields joined by `\n`: ``` v1 {APP_ID} {KEY_ID} {HOST} lowercased {METHOD} uppercased {PATH} no query, NOT url-decoded {CANONICAL_QUERY} sorted, RFC3986-encoded, "" when absent {TIMESTAMP} {NONCE} {SHA256_HEX(RAW_BODY)} sha256("") for GET/DELETE ``` Every field earns its place. `CANONICAL_QUERY` is in there because without it `?limit=1` and `?limit=100000` sign identically, so a captured read signature could be replayed to dump everything. `HOST` stops a signature captured against one deployment replaying into another. The timestamp window is **asymmetric**: `-120s <= now - ts <= +30s`. A symmetric window is a ten-minute replay window, and there is no legitimate reason to sign in the future beyond small clock skew. A working reference implementation is in `docs/TENANT_INTEGRATION.md`, and `scripts/sign_request.mjs` signs a request from the terminal. ## Idempotency `Idempotency-Key` is **required** on every money-moving POST. A missing key is a 400 — the server never invents one, because a server-generated key is unique per request and protects nothing, which is worse than none because it looks like protection. - Replaying a completed key returns the **original response verbatim**, with its original status code. No second provider call. - The same key with **different parameters** is a 422, never a replay. - A concurrent duplicate is a 409 `request_in_progress`. ## Errors Branch on `error.code` and the three booleans, never on the HTTP status: `terminal` (reverse and tell the user), `retriable` (retry with the same key), `ambiguous` (**do not reverse** — poll instead). ## Amounts Integer minor units, with a per-currency exponent. **UGX, RWF, XAF and XOF are zero-decimal**: 2000 UGX is `2000`. Getting this wrong is a 100x error. ## Test mode is NOT a sandbox **Every request reaches a real provider. There is no sandbox, and no test host.** AptaPay routes to a single upstream provider, and that provider publishes exactly one API host for live and test traffic alike. No sandbox base URL exists anywhere in its reference documentation. So "test mode" here does not mean what it means on Stripe. It is a **second, real provider account** holding a small real balance, reached over the same wire as production. A test-mode payout moves real money out of a real wallet to a real phone number. It cannot be reversed, because the provider exposes no refund endpoint. | | What you might expect | What actually happens | | --- | --- | --- | | Host | a separate sandbox host | the one production host, always | | Money | simulated | real, in a real wallet | | Recipients | fake numbers accepted | real MSISDNs, really credited | | Undo | reverse the test charge | none — no refund endpoint exists | Two guardrails stand in for the sandbox, and they are permanent, not temporary scaffolding: - **A hard amount ceiling on every test-mode transaction**, enforced by this gateway *before* any provider call. Over it, you get a `422` and no request ever leaves. - **`is_test_mode` stamped on every transaction record**, so a test transaction is identifiable forever after the fact. Mode is a property of **which credentials you hold**, never of a request field — there is no `test: true` to send, and no header that switches it. A live key transacts live; that is the only thing that decides it. See `GET /healthz` for which mode a deployment is running. ## CORS There isn't any, deliberately. This is a server-to-server API and browsers must never call it: signing from client-side JS would put your secret in view-source. Cross-origin browser requests are denied. servers: - url: https://api.pay.aptahq.com description: >- Production. There is no sandbox host, because the upstream provider has none — see "Test mode is NOT a sandbox". Sign the host you dial: the host is part of the canonical string, so a request dialled here must claim `api.pay.aptahq.com`. security: - AptaPaySignature: [] tags: - name: Collections description: Money in. - name: Payouts description: Money out. - name: Refunds description: Reversals — 501 where the routed provider has no refund endpoint. - name: Transactions description: The gateway's own ledger of what it was asked to do. - name: Beneficiaries description: Saved recipients. Stored masked, names re-resolved at payout time. - name: Reference description: Corridors, banks, countries, balances, capability matrix. - name: Float description: Your own claim on the shared wallet pool — what you can actually pay out. - name: FX description: Exchange between your own wallets. Quote is free; exchange moves money. - name: Webhooks description: Provider ingress. Documented for completeness; tenants never call it. - name: Ops description: Health. paths: /v1/collections/{reference}/authorize: post: tags: - Collections summary: OTP / PIN / 3DS step description: > **Finish a charge that came back `requires_action`.** When a collection needs a second step from the customer — an SMS OTP, a momo PIN, a 3-D Secure result — you collect that value in your UI and submit it here against the transaction's gateway reference. Returns the updated transaction. The status may still be `pending` afterwards: authorizing proves the customer consented, it does not prove the provider has settled, so keep watching the webhook or poll `GET /v1/collections/{reference}`. **This call validates the code AND charges.** With the upstream provider there is no separate "authorize" step — authorizing re-sends the charge with the code attached, so a correct code debits the customer immediately: they get the handset PIN prompt (STK push), and success or failure arrives by webhook. Expect `pending` here and treat the webhook as the answer. `pin_id` comes from the `next_action` on the charge (or from `POST /v1/collections/otp` if you drove that yourself); `pin` is what the customer typed. A wrong code fails this call without failing the transaction — prompt again and retry. **`source` must be resupplied.** Re-sending the charge needs the payer's full number, and the gateway never stores one — only its last 4 digits (so a leaked database cannot become a list of customer phone numbers). The `last4` of what you send is checked against the transaction, so a reference cannot be redirected to a different payer. The amount, currency and country come from the stored transaction and cannot be changed here. operationId: authorizeCollection parameters: - name: reference in: path required: true schema: type: string requestBody: required: true content: application/json: schema: type: object properties: authorization: type: object description: >- The provider-agnostic envelope. Branch on the `next_action.type` you were given and post the matching payload back — the wrapper is the same on every rail. properties: type: type: string enum: - otp - pin otp: type: object description: >- `pin_id` identifies which code the customer is answering. `pin` is the code; `code` is accepted as an alias for it. properties: pin_id: type: string pin: type: string code: type: string source: $ref: '#/components/schemas/CollectionSource' description: >- REQUIRED for a momo authorize — the payer, resupplied. Its last 4 digits must match the transaction. otp: type: object description: Legacy unwrapped form. Still accepted. properties: pin_id: type: string pin: type: string pin: type: string example: authorization: type: otp otp: pin_id: '{{otp_pin_id}}' pin: '{{otp_pin}}' source: type: momo msisdn: '+256763494235' network: MTN country: UG responses: '200': description: >- The code was accepted and the charge placed. `pending` means the customer now has the handset PIN prompt; watch the webhook. content: application/json: schema: $ref: '#/components/schemas/APIResult' '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' components: schemas: CollectionSource: oneOf: - $ref: '#/components/schemas/CollectionMomoSource' - $ref: '#/components/schemas/BankDestination' discriminator: propertyName: type APIResult: type: object description: > The single response envelope, used by EVERY endpoint so a consuming app parses one shape everywhere. required: - code - message properties: code: type: integer example: 200 message: type: string example: OK data: description: Present on success. Shape varies per endpoint. error: $ref: '#/components/schemas/GatewayErrorBody' CollectionMomoSource: type: object description: > A momo source on a COLLECTION. `country` is optional here and defaults to the request's top-level `country`. Collections pull money: a wrong corridor fails or produces a refundable charge, so inheriting is safe. The payout side is deliberately stricter — see `PayoutMomoDestination`. required: - type - msisdn properties: type: type: string enum: - momo msisdn: type: string description: > The customer's phone number in whatever form they typed it. All of `0772123456`, `256772123456`, `+256772123456` and the bare national `772123456` are accepted, with spaces, dashes and parentheses ignored. The platform normalises to E.164 WITH the leading `+` (`+256772123456`) using the country code of the resolved corridor — so a missing country code is supplied, never guessed from the digits. The number is validated AGAINST the corridor: one carrying a different country's calling code, or the wrong national length, is rejected with `invalid_msisdn` rather than reinterpreted. example: '0772123456' network: type: string description: > Network code, a free string from the corridor table — never a closed enum, so a network can be added in Firestore with no schema change. example: MTN country: type: string description: > Optional. Defaults to the request's top-level `country`. Supply it only to state the number's country explicitly; when present it is still validated against the number, so a mismatch is an error. example: UG BankDestination: type: object required: - type - country - bank_code - account_number properties: type: type: string enum: - bank country: type: string example: NG bank_code: type: string example: '044' bank_name: type: string account_number: type: string example: '0011223344' account_name: type: string description: > Advisory only. The gateway RE-RESOLVES the account name at payout time, every time — a stale "yes, this is Jane Doe" can outlive the account being closed, renamed, or reassigned. msisdn: type: string example: '+256763494235' description: > The RECIPIENT's phone number. Not needed to reach the account, but the upstream provider REQUIRES a contact number on bank payouts and rejects an empty one — so a bank payout routed upstream without this is refused as `validation_failed` naming `destination.msisdn`. Accepted in local format (`0763494235`) and normalised to E.164 against `destination.country`. GatewayErrorBody: type: object description: > Machine-readable error classification. EXACTLY ONE of terminal/retriable/ ambiguous is true. laces_api inferred this from the HTTP status and got it wrong, stranding real money twice (2026-08-15, 2026-08-16). Branch on these booleans, never on the status code: terminal -> the provider refused. Reverse the debit and tell the user. retriable -> safe to retry with the SAME Idempotency-Key. ambiguous -> the outcome is UNKNOWN. Do NOT reverse. Poll instead. required: - code - message - terminal - retriable - ambiguous properties: code: type: string description: Stable machine code. Branch on this, never on `message`. example: payout_rejected_by_provider message: type: string description: > Human text from a compiled-in map. NEVER provider text — a stringified provider error can carry an Authorization header. terminal: type: boolean retriable: type: boolean ambiguous: type: boolean details: type: object additionalProperties: type: string responses: BadRequest: description: Validation failed. content: application/json: schema: $ref: '#/components/schemas/APIResult' Unauthorized: description: > Missing, malformed, stale, replayed or invalid signature. Also returned when a body was sent but its raw bytes were unavailable — verified-as-empty must never mean processed-as-full. content: application/json: schema: $ref: '#/components/schemas/APIResult' securitySchemes: AptaPaySignature: type: apiKey in: header name: X-AptaPay-Signature description: > `v1={hex HMAC-SHA256}` over the ten-field canonical string. Sent alongside `X-AptaPay-Key`, `X-AptaPay-Timestamp` and `X-AptaPay-Nonce` — all four are required. OpenAPI can only model one header per scheme, so the other three are described in the Authentication section above. ````