Build your first API contract - before it breaks

Early-stage B2B SaaS teams often skip formal API contracts because "they're too small." But every line of code you add to your API without guardrails compounds risk.

A machine-readable API contract written in OpenAPI/Swagger becomes a single source of truth which allows you to catch breaking changes pre-merge in your CI and which give you self-documenting APIs that reduce onboarding friction for new engineers, among other benefits.

By formalising your internal API now - when you only have one or two services - you unlock huge efficiency gains down the road. Postman’s 2024 survey found that 5% of teams see API failure rates above 25%. For a three‑engineer startup, that equates to 120 hours saved every month (nearly 1,440 hours per year) - roughly $144,000 in engineering capacity you can reinvest into building new features instead of firefighting.

Get started with your first API contract:

1. Copy the minimal OpenAPI spec from this Gist (syntax-highlighted + copyable): https://gist.github.com/sorenjohanson/8a23a4522f6874e89ef13a136d08655b
2. Add a single CI step to validate it every push.
3. Share the spec with your team as the canonical schema - embed it into your README or internal wiki.

API contracts can take many shapes or form. They can also just be plain README files shared with non-technical colleagues. The most important part is that APIs are clearly defined and that everyone understands each endpoint.

Yours,
Søren

PS: Want to ensure that your APIs never break in production?

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