# REST API Endpoint Designer > Designs RESTful API endpoints following OpenAPI spec and industry best practices. Use when this capability is needed. - Skill: `tomevault-io/rest-api-endpoint-designer` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/rest-api-endpoint-designer` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/rest-api-endpoint-designer/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Integrations & APIs - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/rest-api-endpoint-designer --- # REST API Endpoint Designer ## What this skill does This skill directs the agent to design RESTful API endpoints for a given resource or feature — including URL structure, HTTP methods, request/response schemas, status codes, and error formats. It outputs a complete OpenAPI 3.1 YAML snippet that can be dropped directly into your API spec, along with implementation notes. Use this when starting a new API resource, reviewing an existing endpoint design, or when you want a second opinion on naming conventions and status code choices. ## How to use ### Claude Code / Cursor / Codex Copy this file to `.agents/skills/api-endpoint-designer/SKILL.md` in your project root (for Claude Code), or add the instructions to your `.cursorrules` (for Cursor). Then ask: - *"Design the REST endpoints for a blog post resource using the REST API Endpoint Designer skill."* - *"I need CRUD endpoints for a `team-members` resource. Use the REST API Endpoint Designer skill."* Provide the resource name, any existing conventions in your API (e.g., base path, auth method), and any fields the resource should have. ## The Prompt / Instructions for the Agent When asked to design REST API endpoints, follow these rules: ### 1. URL naming conventions - Use **plural nouns** for resource collections: `/users`, `/orders`, `/blog-posts` - Use **kebab-case** for multi-word resources: `/blog-posts`, not `/blogPosts` - Use path parameters for specific resources: `/users/{userId}` - Use **nested resources** only when the relationship is truly hierarchical: `/users/{userId}/orders` - Avoid verbs in URLs — the HTTP method is the verb: `POST /sessions` not `POST /login` - Use query parameters for filtering, sorting, and pagination: `GET /users?role=admin&sort=created_at&order=desc&page=2&limit=20` ### 2. HTTP method selection | Action | Method | Notes | |---|---|---| | List resources | GET | Paginated, filterable | | Get one resource | GET | By ID in path | | Create | POST | Body contains new resource | | Full replace | PUT | Idempotent — replaces entire resource | | Partial update | PATCH | Only fields provided are updated | | Delete | DELETE | Returns 204 No Content on success | ### 3. Status codes Always return the most specific correct code: - `200` — success with body - `201` — resource created (include `Location` header) - `204` — success with no body (DELETE, some PATCH) - `400` — bad request / validation error (include which field failed) - `401` — not authenticated - `403` — authenticated but not authorized - `404` — resource not found - `409` — conflict (e.g., duplicate email) - `422` — unprocessable entity (semantic validation failed) - `500` — internal server error (never leak stack traces) ### 4. Error response format All error responses must follow this consistent shape: ```json { "error": { "code": "VALIDATION_ERROR", "message": "Human-readable description", "details": [ { "field": "email", "message": "must be a valid email address" } ] } } ``` ### 5. Output format Produce: 1. A table listing each endpoint with method, path, description, and auth requirement 2. An OpenAPI 3.1 YAML snippet for each endpoint 3. Implementation notes (e.g., pagination defaults, required indexes, rate limiting recommendations) ## Example **Input to Agent:** > "Design CRUD endpoints for a `posts` resource. Fields: title (string, required), body (string, required), authorId (string, required), status (draft | published, default: draft). Auth is required for create/update/delete. Use the REST API Endpoint Designer skill." **Output from Agent:** **Endpoints** | Method | Path | Description | Auth Required | |---|---|---|---| | GET | /posts | List posts (paginated, filterable by status) | No | | GET | /posts/{postId} | Get a single post | No | | POST | /posts | Create a new post | Yes | | PATCH | /posts/{postId} | Update post fields | Yes (author only) | | DELETE | /posts/{postId} | Delete a post | Yes (author only) | **OpenAPI YAML** ```yaml paths: /posts: get: summary: List posts operationId: listPosts tags: [Posts] parameters: - name: status in: query schema: type: string enum: [draft, published] - name: page in: query schema: type: integer default: 1 - name: limit in: query schema: type: integer default: 20 maximum: 100 responses: '200': description: Paginated list of posts content: application/json: schema: type: object properties: data: type: array items: $ref: '#/components/schemas/Post' meta: $ref: '#/components/schemas/PaginationMeta' post: summary: Create a post operationId: createPost tags: [Posts] security: - bearerAuth: [] requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/CreatePostInput' responses: '201': description: Post created headers: Location: schema: type: string example: /posts/abc123 content: application/json: schema: $ref: '#/components/schemas/Post' '400': $ref: '#/components/responses/ValidationError' '401': $ref: '#/components/responses/Unauthorized' /posts/{postId}: get: summary: Get a post operationId: getPost tags: [Posts] parameters: - $ref: '#/components/parameters/PostId' responses: '200': content: application/json: schema: $ref: '#/components/schemas/Post' '404': $ref: '#/components/responses/NotFound' patch: summary: Update a post operationId: updatePost tags: [Posts] security: - bearerAuth: [] parameters: - $ref: '#/components/parameters/PostId' requestBody: content: application/json: schema: $ref: '#/components/schemas/UpdatePostInput' responses: '200': content: application/json: schema: $ref: '#/components/schemas/Post' '403': $ref: '#/components/responses/Forbidden' '404': $ref: '#/components/responses/NotFound' delete: summary: Delete a post operationId: deletePost tags: [Posts] security: - bearerAuth: [] parameters: - $ref: '#/components/parameters/PostId' responses: '204': description: Post deleted '403': $ref: '#/components/responses/Forbidden' '404': $ref: '#/components/responses/NotFound' ``` **Implementation Notes** - Index `posts.status` and `posts.authorId` for the list endpoint filters - Enforce `limit <= 100` server-side, not just in the spec - `PATCH /posts/{postId}` should check `authorId === currentUser.id` before applying changes — return `403` if not - Consider a `GET /posts?authorId={userId}` filter for profile pages ## Notes - By default this skill outputs OpenAPI 3.1 YAML. Ask for JSON or an earlier version (3.0, 2.0/Swagger) if needed. - The skill does not generate implementation code — only the API contract. Use the Unit Test Writer or another skill for implementation. - For GraphQL or gRPC APIs, this skill is not the right tool — it is designed for REST only. --- > Source: [Notysoty/openagentskills](https://github.com/Notysoty/openagentskills) — distributed by [TomeVault](https://tomevault.io).