Use Cursor's Background Agents to Write Documentation While You Sleep

Problem: Documentation is Always Outdated

You ship features fast, but documentation lags weeks behind. Your team wastes hours explaining code that could document itself.

You'll learn:

• How to set up Cursor agents for overnight documentation runs
• Which files to target for maximum impact
• How to review and merge AI-generated docs safely

Time: 20 min setup, runs while you sleep | Level: Intermediate

Why This Works

Cursor's agent mode (released December 2025) can process entire codebases with multi-file context. Unlike chat, agents can:

• Read your entire project structure
• Follow documentation templates
• Run in the background without VS Code open
• Commit changes to branches automatically

Common use cases:

• API endpoint documentation
• Function/class JSDoc comments
• README updates after refactors
• Migration guides between versions

Solution

Step 1: Install Cursor Agent CLI

# Requires Cursor Pro subscription
npm install -g @cursor/agent-cli

# Verify installation
cursor-agent --version

Expected: Version 0.3.0 or higher

If it fails:

• Error: "Not a Pro subscriber": Upgrade at cursor.sh/pricing
• Command not found: Restart Terminal, check PATH includes npm globals

Step 2: Create Agent Configuration

Create .cursor/agent-config.json in your project root:

{
  "name": "doc-writer",
  "schedule": "0 2 * * *",
  "task": "document-codebase",
  "context": {
    "include": ["src/**/*.ts", "src/**/*.tsx"],
    "exclude": ["**/*.test.ts", "**/*.spec.ts"],
    "maxFiles": 50
  },
  "prompt": "Add JSDoc comments to all exported functions and classes. Follow the template in CONTRIBUTING.md. Focus on public APIs.",
  "output": {
    "branch": "docs/auto-{{date}}",
    "commitMessage": "docs: auto-generated documentation",
    "createPR": true
  }
}

Why these settings:

• schedule: Runs at 2 AM daily (cron format)
• maxFiles: Prevents token overload on large codebases
• createPR: Lets you review before merging

Step 3: Add Documentation Template

Create CONTRIBUTING.md with your doc style:

## Documentation Style

### Functions
\```typescript
/**
 * Brief description of what it does
 * 
 * @param paramName - What this parameter does
 * @returns What the function returns
 * @throws {ErrorType} When this error occurs
 * 
 * @example
 * \```ts
 * const result = myFunction("input");
 * \```
 */
\```

### Classes
- Document constructor parameters
- Explain class purpose in one sentence
- Add @example for common usage

This gives the agent a pattern to follow instead of generic AI-style docs.

Step 4: Start the Agent

# Run immediately (test mode)
cursor-agent run .cursor/agent-config.json

# Schedule for background runs
cursor-agent schedule .cursor/agent-config.json

# Check scheduled agents
cursor-agent list

Expected: Agent runs, creates branch docs/auto-2026-02-10, opens PR

Step 5: Review the Output

# Checkout the agent's branch
git fetch origin
git checkout docs/auto-2026-02-10

# Review changes
git diff main...docs/auto-2026-02-10

Look for:

• ✅ Accurate parameter descriptions
• ✅ Realistic examples
• ✅ Consistent formatting
• ❌ Hallucinated function names
• ❌ Copy-pasted descriptions

Merge only after spot-checking - agents can miss context.

Advanced: Target Specific Files

Document Only Changed Files

{
  "name": "doc-changed-files",
  "trigger": "on-commit",
  "context": {
    "include": ["{{git.modified}}"],
    "maxFiles": 10
  },
  "prompt": "Update documentation for changed functions only"
}

This runs after each commit, documenting only what you touched.

Generate API Docs from OpenAPI

{
  "name": "api-docs",
  "schedule": "0 3 * * 1",
  "task": "generate-docs",
  "context": {
    "include": ["openapi.yaml", "docs/api-template.md"]
  },
  "prompt": "Generate API documentation using the template. Include curl examples for each endpoint.",
  "output": {
    "path": "docs/api-reference.md",
    "branch": "main"
  }
}

Runs weekly (Mondays at 3 AM), updates docs from your OpenAPI spec.

Verification

# Check agent ran successfully
cursor-agent logs doc-writer

# See last run status
cursor-agent status

You should see: Exit code 0, PR created, no timeout errors

If it times out:

• Reduce maxFiles to 25
• Split into multiple agents by directory
• Exclude large generated files

What You Learned

• Cursor agents can run scheduled tasks without VS Code open
• Templates in your repo guide AI output quality
• Always review auto-generated docs before merging
• Best for: repetitive doc tasks, not architectural explanations

Limitations:

• Agents don't understand business context
• Can hallucinate if code is ambiguous
• Requires Cursor Pro ($20/month)

When NOT to use:

• Complex architecture decisions
• Security-sensitive code explanations
• User-facing product documentation

Tested on Cursor 0.43.0, macOS & Linux, with TypeScript/React projects