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mern-api-docs

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Generate OpenAPI documentation from Zod schemas and API routes.

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How to use this skill

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  2. Copy the prompt below and paste it into your agent.
  3. Review the proposed files and risks before you approve installation.
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I want to install this Agent Skill for this project in Codex.

Source SKILL.md: https://github.com/majiayu000/claude-skill-registry/blob/HEAD/skills/development/mern-api-docs/SKILL.md

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Purpose

Generate and serve OpenAPI (Swagger) documentation derived from Zod schemas and Next.js API routes.

Arguments

  • --serve — Start Swagger UI at /api/docs
  • --export <path> — Export OpenAPI spec to file (default: openapi.json)
  • (no args) — Generate spec and report endpoints documented

What gets created

apps/web/
├── app/api/docs/route.ts           # Swagger UI endpoint
├── src/lib/openapi.ts              # OpenAPI spec generator
└── openapi.json                    # Generated spec (if --export)

How it works

  1. Scans packages/shared/schemas/ for Zod schemas
  2. Scans apps/web/src/app/api/ for route handlers
  3. Extracts request/response types from Zod schemas
  4. Generates OpenAPI 3.0 spec with:
    • Endpoints from file structure
    • Request bodies from Create*Schema
    • Response schemas from *ResponseSchema
    • Query params from *QuerySchema
    • Path params from [id] segments

Schema conventions for docs

// packages/shared/schemas/todo-item.ts

/** @description Create a new todo item */
export const CreateTodoItemSchema = z.object({
  /** @description Item title (required) */
  title: z.string().min(1).max(200),
  /** @description Optional description */
  description: z.string().optional(),
});

/** @description Todo item response */
export const TodoItemSchema = z.object({
  id: z.string(),
  title: z.string(),
  // ...
});

JSDoc comments become OpenAPI descriptions.

Swagger UI

When --serve is used, Swagger UI is available at /api/docs:

  • Interactive API explorer
  • Try-it-out functionality (with auth)
  • Schema visualization

Workflow

  1. Ensure schemas follow naming conventions
  2. Run skill to generate/update spec
  3. Review generated documentation
  4. Optionally serve Swagger UI

Output

  • Endpoints documented count
  • Schemas extracted count
  • Missing documentation warnings
  • Spec file location (if exported)

Reference

For setup and customization, see reference/mern-api-docs-reference.md