The Non‑Technical Founder’s API & Integration Checklist

Engineers don’t want to guess. Missing or ambiguous details drive clarifying tickets, rework and feature drift. A concise spec that covers endpoints, request/response examples, auth, and failure modes short‑circuits those conversations and gives the team a testable target.

Good specs are not full developer docs — they’re a contract. Think of the one‑page spec as the agreement between product and engineering: what will be built, how success is measured, and what counts as done. That lets developers mock endpoints, run contract tests, and scope work precisely.

Fill these items before the first engineering meeting. They’re deliberately practical — minimal words, concrete examples, and a single success test for each endpoint. Treat each endpoint as a small contract: name, purpose, method, path, sample request, sample response, success criteria, and failure cases.

Include authentication and operational limits on the same page. Engineers will ask about auth (API keys, OAuth, JWT), rate limits, and whether retries should be attempted on 5xx vs 4xx errors. If the integration will move production data, note data sensitivity and retention rules up front.

Before (vague): “We need to push every sale to Stripe.” That leaves engineers guessing what fields, how to dedupe, and what ‘every’ means. After (clear): include the endpoint, sample JSON of the sale, which field is the unique id, required timestamp format, and the acceptance test (e.g., “Given sale XYZ exists, a POST returns 201 and a body with transfer_id”).

Provide an explicit failure policy: e.g., “On 409 duplicate, client should mark as already-sent and not retry; on 5xx, retry with exponential backoff up to 3 attempts.” That one sentence prevents hours of back‑and‑forth and unexpected retry storms in production.

Mistake: assuming developers will infer business rules. Example—'send every order' may mean all orders or only paid orders. Solution: name the filter explicitly and provide sample payloads that include the edge cases (refunds, test orders).

Mistake: under‑specifying auth and access. If the integration requires third‑party credentials (Stripe, Shopify), specify who will grant access and whether a sandbox account is available. Without this, engineers can’t run end‑to‑end tests and progress stalls.

End with a short delivery checklist the team can tick off. Each endpoint should have: a working mock, automated contract or integration test, documented sample payloads, and a labeled Postman/Insomnia collection or OpenAPI snippet so QA can run the same flows.

Define a clear acceptance test per endpoint (one or two sentences). Example: “When POST /v1/lead with valid payload is called, system returns 201 and email field in response equals request.email; the lead appears in CRM within 10 seconds.” Concrete tests stop debates at demo time.