How to Auto-Generate Documentation with Claude Code

Reduce the Documentation Burden to Zero

We all know documentation matters, but it’s easy to put off. With Claude Code, you can auto-generate documentation from code and keep it up to date.

Automatic JSDoc / TSDoc

> Add JSDoc comments to every public function under src/.
> Include parameters, return values, and a usage example.

/**
 * Search for users and return the results.
 *
 * @param query - The search query string
 * @param options - Search options
 * @param options.page - Page number (default: 1)
 * @param options.limit - Items per page (default: 20)
 * @param options.sortBy - Field to sort on
 * @returns The search results and pagination info
 *
 * @example
 * ```typescript
 * const result = await searchUsers("Tanaka", { page: 1, limit: 10 });
 * console.log(result.data); // User[]
 * console.log(result.meta.total); // total count
 * ```
 */
async function searchUsers(
  query: string,
  options: SearchOptions = {}
): Promise<PaginatedResult<User>> {
  // implementation
}

Generating API Specifications

Have Claude Code auto-generate an OpenAPI spec from the code.

> Analyze the API endpoints under src/routes/ and
> generate an OpenAPI 3.0 specification.
> Include request and response types.

openapi: "3.0.3"
info:
  title: "Task Management API"
  version: "1.0.0"
  description: "Task management application API"

paths:
  /api/tasks:
    get:
      summary: "Get the list of tasks"
      parameters:
        - name: page
          in: query
          schema:
            type: integer
            default: 1
        - name: status
          in: query
          schema:
            type: string
            enum: [todo, in_progress, done]
      responses:
        "200":
          description: "Success"
          content:
            application/json:
              schema:
                type: object
                properties:
                  data:
                    type: array
                    items:
                      $ref: "#/components/schemas/Task"
                  meta:
                    $ref: "#/components/schemas/Pagination"

    post:
      summary: "Create a task"
      security:
        - bearerAuth: []
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/CreateTaskInput"
      responses:
        "201":
          description: "Created successfully"

Generating the README

Auto-generate a README from the project structure.

> Analyze the project structure and generate a README.
> Include setup instructions, development commands, directory layout,
> and environment variable documentation.

Architecture Documentation

> Analyze the project architecture and create a document
> describing the directory layout and data flow.

# Architecture Overview

## Directory Layout
src/
├── app/          # Next.js App Router pages
├── components/   # UI components
│   ├── ui/       # Generic UI pieces
│   └── features/ # Feature-specific components
├── lib/          # Utilities and setup
│   ├── db.ts     # Database connection
│   ├── auth.ts   # Authentication logic
│   └── api.ts    # API client
└── types/        # Type definitions

## Data Flow
1. Client -> Server Component -> Prisma -> PostgreSQL
2. Client -> API Route -> Service Layer -> Repository -> DB

Auto-Generating a Changelog

> Analyze the git log since the last release and
> generate CHANGELOG entries.
> Categorize them into Features, Bug Fixes, and Breaking Changes.

## [1.3.0] - 2026-04-01

### Features
- Added a sales chart to the dashboard (#142)
- Implemented bulk task operations (#138)

### Bug Fixes
- Fixed filter conditions being reset (#145)
- Fixed timezone bugs in date display (#143)

### Breaking Changes
- Unified the API response format (v1 API is now deprecated)

Improving Comment Quality

> Review existing comments and fix inaccurate ones,
> and add explanations to complex logic.
> Remove obvious comments (e.g., `i++; // increment i`).

When combined with automated Git operations, you can even auto-generate a CHANGELOG from commit messages. See completely automating Git operations. Writing documentation rules in CLAUDE.md keeps things consistent. For how to write one, see the complete CLAUDE.md guide.

Setting Documentation Rules in CLAUDE.md

## Documentation Rules
- Every public function must have JSDoc
- When adding a new API endpoint, also update the OpenAPI spec
- Add inline comments to complex logic
- Obvious comments are unnecessary

Summary

Automating documentation generation with Claude Code prevents drift between code and docs. Generate JSDoc, API specs, and architecture documents directly from the code to keep the information always accurate.

For documentation generation details, see the official TypeDoc site, and for Claude Code, see the official Anthropic documentation.