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What good API documentation does
Documentation is the user interface of an API. Developers judge an API by how quickly they can make their first successful call, and that depends almost entirely on the docs. When documentation is missing, vague or out of date, every integration turns into meetings, emails and guesswork — and your own developers spend their time answering questions instead of building.
Good documentation has two layers. A machine-readable OpenAPI specification describes every endpoint, parameter and response exactly, and can power interactive reference pages and client generators. Alongside it, readable guides explain the concepts, the typical workflows and the gotchas that a reference page alone never covers.
Who needs it
- A SaaS startup opening its API to customers or integration partners.
- A real estate portal onboarding brokers who will push listings through an API.
- An e-commerce platform giving marketplaces or logistics partners access to orders.
- A manufacturer sharing a distributor API with outside IT teams.
- Any business with an internal API that new developers keep struggling to learn.
Warning signs: partners ask the same questions repeatedly, the only documentation is a shared document last updated long ago, error codes aren’t explained anywhere, or developers rely on reading the source code to understand the API.
What’s included
- An OpenAPI specification covering every endpoint, request, response and error.
- A getting-started guide that takes a developer from credentials to a first successful call.
- Authentication explained step by step, including token expiry and refresh.
- Error formats and what each error code means and how to handle it.
- Rate limits, pagination and versioning rules.
- Working request and response examples for the most common workflows.
- Webhook event descriptions and payload examples, where your API sends events.
- A changelog so integrators can see what changed between versions.
How we produce it
- Review the API. We read the code and exercise the endpoints to confirm how they actually behave.
- Write or correct the spec. Existing OpenAPI files are checked against real behaviour; missing ones are written.
- Write the guides, starting with the flows integrators need most.
- Test the docs. Every example is run against a test environment, so nothing in the guide is broken.
- Automate. The spec lives in the repository and is checked in the build, so drift between docs and code is caught early.
Keeping documentation current
Documentation usually goes out of date because it lives somewhere separate from the code. We keep the specification and guides in the same repository as the API, so a change to an endpoint and a change to its documentation go through the same review. Where the stack supports it, the spec can be validated automatically against the implementation, so a mismatch fails the build rather than reaching a partner.
What affects timeline and cost
- The size of the API and how many workflows need guides.
- Whether a usable OpenAPI spec already exists.
- How consistent the API itself is — inconsistent APIs take more explaining.
- Whether a test environment is available for verifying examples.
- Hosting needs, such as a public developer portal versus internal docs.
After reviewing the API, we give you a clear scope and estimate before writing begins.
Common mistakes
- Auto-generated reference pages with no explanation of concepts or workflows.
- Examples that were never run and don’t work.
- Undocumented errors, leaving integrators to guess what went wrong.
- Documentation stored in a separate tool that nobody updates.
- Writing for the team that built the API rather than for someone seeing it for the first time.
A simple test catches most of these: give the documentation to a developer who has never seen the API and watch where they get stuck. Every question they have to ask is a gap worth filling, and we use exactly this kind of review before calling documentation finished.
Frequently asked questions
Can you document an API we already have?
Yes. We review the code and test the endpoints to document what the API actually does, and we flag any inconsistencies we find along the way.
What is an OpenAPI specification?
It’s a standard, machine-readable description of a REST API. Tools can turn it into interactive reference pages, generate client code and validate requests, which is why it’s the foundation of most modern API documentation.
Where will the documentation be hosted?
That’s your choice — a public developer page on your website, a private portal for partners, or internal pages for your own team. The source files stay in your repository either way.
How do you stop the docs going out of date?
By keeping them in the same repository as the code, reviewing them with each change, and validating the spec automatically where possible.
Can the OpenAPI spec generate client libraries for partners?
Yes. A complete, accurate spec can be used with widely available generator tools to produce starter client code in several languages. Generated code still benefits from review, but it gives partners a faster start.
Talk to us about api documentation
OpenAPI specs and readable guides, so integrating doesn't require a phone call.