API Documentation Template

Document REST API endpoints with architecture overview, request/response JSON examples using syntax-highlighted code blocks. Perfect for API design reviews and developer onboarding.

Use this template

What you get

Architecture overview with Client, API Server, and Database nodes
Syntax-highlighted JSON code blocks for request and response bodies
Multiple endpoint sections with clear visual separation

What this template is for

API documentation that lives in a diagram is easier to discuss and faster to update than a wall of text. This template helps you map REST endpoints, HTTP methods, request/response structures, and authentication flows in a visual format that both developers and product managers can understand.

When to use this template

Design a new REST API by mapping resources and their relationships before writing any code.
Onboard new developers by giving them a visual map of all available endpoints.
Plan an API version migration by comparing v1 and v2 endpoint structures side by side.
Document microservice communication patterns across your system architecture.

How to use it

1List all resources (e.g., Users, Orders, Products) as top-level nodes.
2Under each resource, add the available HTTP methods: GET, POST, PUT, DELETE.
3Document request parameters, authentication requirements, and response formats for each endpoint.
4Draw relationships between related resources — orders belong to users, products belong to categories.
5Review with the team: are all error responses documented? Are rate limits noted?

Quick example

User API endpoints

GET /users — List all users

GET /users/:id — Get single user

POST /users — Create user

PUT /users/:id — Update user

DELETE /users/:id — Delete user

How it compares to similar tools

API Docs vs OpenAPI Spec

An OpenAPI spec is a machine-readable definition that can generate docs automatically. A visual API diagram is a design tool — you draw it during the planning phase, before writing the spec. They complement each other: diagram first for design, spec second for automation.

Common mistakes to avoid

Documenting only the happy path
Every endpoint should document its error responses — 400, 401, 404, 500. Developers integrating with your API need to know what can go wrong, not just what happens when everything works.

Frequently asked questions

Should I use a diagram or a tool like Swagger?+

Use a diagram during the design phase when endpoints are still being debated. Switch to Swagger or OpenAPI once the API is stable enough to generate documentation automatically. The diagram is a thinking tool; Swagger is a publishing tool.