Ask Claude to Generate an OpenAPI Spec from Your Existing API Endpoints

Your API documentation is probably out of date. Claude reads the actual code and generates an OpenAPI spec that matches what the API really does right now.

"Read all my API routes and controllers, then generate a complete OpenAPI 3.1 spec"

Claude traces each route through your code — the HTTP method, URL parameters, query parameters, request body validation, response structures, middleware (auth, rate limits), and status codes — then assembles it into a proper OpenAPI document.

# Claude generates specs like this from your actual code:
paths:
  /api/users/{id}:
    get:
      summary: Get user by ID
      parameters:
        - name: id
          in: path
          required: true
          schema:
            type: integer
      responses:
        '200':
          description: User found
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/User'
        '404':
          description: User not found

You can scope and customize the output:

# Just the public endpoints
"Generate an OpenAPI spec for only the public-facing API routes (no admin endpoints)"

# With examples
"Include realistic example values for every request and response field"

# Specific format
"Output the spec in JSON format, not YAML"

# Grouped by feature
"Organize the endpoints by tag — users, orders, products, payments"

After generating the spec, Claude can also:

• Validate it — check for inconsistencies between the spec and actual code behavior
• Add missing descriptions — write clear summaries for every endpoint and parameter
• Generate a Postman collection — convert the spec into an importable collection
• Update an existing spec — diff your old spec against the current code and patch the differences

The best API docs are generated from code, not written from memory — Claude reads your endpoints and writes the spec that matches.

via Claude Code