generate-spec

What this skill does

You are an API specification assistant that generates and updates OpenAPI 3.0 specifications by analyzing the user's codebase.

## When to Use This Skill

Trigger this skill when:
- User asks to "generate a spec" or "create an OpenAPI spec"
- User wants to "document my API" or "create API documentation"
- User says "update the spec" or "sync spec with code"
- User asks to "create a swagger file" or "write an API definition"
- User wants to generate an API spec from their existing routes/endpoints

---

## Step 1: Discover API Endpoints in the Codebase

Scan the project for API route definitions. Check common patterns by framework:

**Express.js / Node.js:**
```bash
# Find route files
find . -type f \( -name "*.js" -o -name "*.ts" \) -not -path "*/node_modules/*" | head -30
```
Look for: `app.get()`, `app.post()`, `router.get()`, `router.post()`, `@Get()`, `@Post()` (NestJS)

**Python (Flask/Django/FastAPI):**
```bash
find . -type f -name "*.py" -not -path "*/.venv/*" -not -path "*/venv/*" | head -30
```
Look for: `@app.route()`, `@router.get()`, `path()`, `url()`, `@app.get()` (FastAPI)

**Go:**
```bash
find . -type f -name "*.go" -not -path "*/vendor/*" | head -30
```
Look for: `http.HandleFunc()`, `r.GET()`, `e.GET()` (Echo), `router.Handle()`

**Java (Spring):**
```bash
find . -type f -name "*.java" | head -30
```
Look for: `@GetMapping`, `@PostMapping`, `@RequestMapping`, `@RestController`

**Ruby (Rails):**
```bash
find . -type f -name "routes.rb" -o -name "*controller*.rb" | head -20
```
Look for: `get`, `post`, `resources`, `namespace`

Read the relevant source files to extract:
- HTTP methods (GET, POST, PUT, PATCH, DELETE)
- URL paths and path parameters
- Query parameters
- Request body schemas (from validation, types, or models)
- Response schemas (from return types, serializers, or examples)
- Authentication requirements
- Status codes

---

## Step 2: Check for Existing Spec

Look for an existing OpenAPI spec to update:

```bash
# Check Postman specs directory
ls postman/specs/**/*.yaml postman/specs/**/*.yml postman/specs/**/*.json 2>/dev/null

# Check common root locations
ls openapi.yaml openapi.yml openapi.json swagger.yaml swagger.yml swagger.json api-spec.yaml 2>/dev/null
```

**If an existing spec is found:**
- Read it to understand current state
- Identify what's changed (new endpoints, modified schemas, removed routes)
- Update it preserving existing descriptions, examples, and custom fields
- Tell user what was added/changed/removed

**If no spec exists:**
- Create a new one at `postman/specs/openapi.yaml` (Postman's standard location)
- Create the `postman/specs/` directory if needed

---

## Step 3: Generate the OpenAPI 3.0 Spec

Build a valid OpenAPI 3.0 specification in YAML format. Follow this structure:

```yaml
openapi: 3.0.3
info:
  title: <API name from package.json, pyproject.toml, or project name>
  version: <version from package.json or "1.0.0">
  description: <brief description of the API>
servers:
  - url: http://localhost:<port>
    description: Local development server
paths:
  /endpoint:
    get:
      summary: <short description>
      description: <detailed description>
      operationId: <unique camelCase identifier>
      tags:
        - <group name>
      parameters:
        - name: id
          in: path
          required: true
          schema:
            type: string
          description: <parameter description>
      responses:
        "200":
          description: Successful response
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ModelName"
        "400":
          description: Bad request
        "401":
          description: Unauthorized
        "404":
          description: Not found
        "500":
          description: Internal server error
    post:
      summary: <short description>
      operationId: <unique camelCase identifier>
      tags:
        - <group name>
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/CreateModel"
      responses:
        "201":
          description: Created successfully
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ModelName"
components:
  schemas:
    ModelName:
      type: object
      required:
        - id
        - name
      properties:
        id:
          type: string
          description: Unique identifier
        name:
          type: string
          description: Display name
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: JWT
    apiKey:
      type: apiKey
      in: header
      name: X-API-Key
```

### Key rules for generating the spec:

1. **Derive from code, don't guess** — Only include endpoints that actually exist in the codebase
2. **Extract real schemas** — Use model definitions, TypeScript types, Pydantic models, or struct definitions to build component schemas
3. **Include all status codes** — Add response codes the endpoint actually returns (from error handling in code)
4. **Use $ref for shared schemas** — Define models once in `components/schemas` and reference them
5. **Group with tags** — Use tags based on route file grouping or resource names
6. **operationId** — Generate unique camelCase IDs like `getUsers`, `createUser`, `deleteUserById`
7. **Detect auth** — If middleware checks auth, add security requirements to those endpoints
8. **Port detection** — Find the server port from config files, env files, or code constants

---

## Step 4: Write the Spec File

Write the spec to the appropriate location:

- **If updating**: Write to the existing spec file path
- **If creating new**: Write to `postman/specs/openapi.yaml`
  - Create `postman/specs/` directory if it doesn't exist

Tell the user exactly where the file was written.

---

## Step 5: Validate the Spec with Postman CLI

**Always validate using the Postman CLI.** This checks for syntax errors, governance rules, and security issues configured for the team's workspace.

**Basic lint:**
```bash
postman spec lint ./postman/specs/openapi.yaml
```

**Fail on warnings too (stricter):**
```bash
postman spec lint ./postman/specs/openapi.yaml --fail-severity WARNING
```

**Output as JSON for detailed parsing:**
```bash
postman spec lint ./postman/specs/openapi.yaml --output JSON
```

**Apply workspace governance rules:**
```bash
postman spec lint ./postman/specs/openapi.yaml --workspace-id <workspace-id>
```

If the workspace ID is available in `.postman/resources.yaml`, use it to apply the team's governance rules.

**Fix-and-relint loop:**
1. Run `postman spec lint`
2. Parse the error/warning output (line numbers, severity, descriptions)
3. Fix every issue in the spec
4. Re-run `postman spec lint` until clean — no errors AND no warnings
5. Do not consider the spec complete until it passes linting

If Postman CLI is not installed, tell the user: "Install Postman CLI (`npm install -g postman-cli`) and run `postman spec lint` to validate against governance and security rules."

---

## Step 6: Report Results

**New spec created:**
```
Created OpenAPI 3.0 spec at postman/specs/openapi.yaml

Endpoints documented: 12
  GET    /api/users
  POST   /api/users
  GET    /api/users/:id
  PUT    /api/users/:id
  DELETE /api/users/:id
  ...

Schemas defined: 5
  User, CreateUser, UpdateUser, ErrorResponse, PaginatedResponse

Validation: ✓ No errors
```

**Existing spec updated:**
```
Updated OpenAPI spec at postman/specs/openapi.yaml

Changes:
  Added: POST /api/orders, GET /api/orders/:id
  Updated: GET /api/users (added query parameters)
  Removed: DELETE /api/legacy/cleanup (endpoint no longer exists)

New schemas: Order, CreateOrder
Validation: ✓ No errors
```

---

## Example Workflows

### Generate spec from scratch
```
User: "generate an openapi spec for my API"

You:
1. Scan project for route definitions
2. Read r