MCPInstall

api-designer

by jeffallanBackend & APIs

Use when designing REST or GraphQL APIs, creating OpenAPI specifications, or planning API architecture. Invoke for resource modeling, versioning strategies, pagination patterns, error handling standards.

Installs
6.5K
Last 24h
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#4387
Security
Fail

Install

Works with every agent the skills CLI supports.

npx skills add https://github.com/jeffallan/claude-skills --skill api-designer
  1. 01

    Install

    Run the command in your project. The CLI asks which agents to install for.

  2. 02

    Describe the task

    Ask your agent for something this skill covers. It loads api-designer automatically when relevant.

  3. 03

    Review the result

    The agent follows the SKILL.md steps, scripts and references bundled with the skill.

Security audits

Independent scans of the skill's instructions and bundled files.

Gen Agent Trust Hub FailCRITICAL ·The skill provides comprehensive guidance for API design but includes a documentation URL flagged as malicious by automated security scans. It also recommends using external tools via npx, which involves downloading and executing third-party code from the npm registry.
Socket PassNo alerts
Snyk WarnMEDIUM ·Risk: MEDIUM · 1 issue
Runlayer PassNONE ·6 files scanned · No issues
ZeroLeaks PassNONE ·Score: 93/100 · 2 sections analyzed

SKILL.md

The instructions your agent reads when the skill is triggered.

API Designer

Senior API architect specializing in REST and GraphQL APIs with comprehensive OpenAPI 3.1 specifications.

Core Workflow

  1. Analyze domain — Understand business requirements, data models, and client needs
  2. Model resources — Identify resources, relationships, and operations; sketch entity diagram before writing any spec
  3. Design endpoints — Define URI patterns, HTTP methods, request/response schemas
  4. Specify contract — Create OpenAPI 3.1 spec; validate before proceeding: npx @redocly/cli lint openapi.yaml
  5. Mock and verify — Spin up a mock server to test contracts: npx @stoplight/prism-cli mock openapi.yaml
  6. Plan evolution — Design versioning, deprecation, and backward-compatibility strategy

Reference Guide

Load detailed guidance based on context:

TopicReferenceLoad When
REST Patternsreferences/rest-patterns.mdResource design, HTTP methods, HATEOAS
Versioningreferences/versioning.mdAPI versions, deprecation, breaking changes
Paginationreferences/pagination.mdCursor, offset, keyset pagination
Error Handlingreferences/error-handling.mdError responses, RFC 7807, status codes
OpenAPIreferences/openapi.mdOpenAPI 3.1, documentation, code generation

Constraints

MUST DO

  • Follow REST principles (resource-oriented, proper HTTP methods)
  • Use consistent naming conventions (snake_case or camelCase — pick one, apply everywhere)
  • Include comprehensive OpenAPI 3.1 specification
  • Design proper error responses with actionable messages (RFC 7807)
  • Implement pagination for all collection endpoints
  • Version APIs with clear deprecation policies
  • Document authentication and authorization
  • Provide request/response examples

MUST NOT DO

  • Use verbs in resource URIs (use /users/{id}, not /getUser/{id})
  • Return inconsistent response structures
  • Skip error code documentation
  • Ignore HTTP status code semantics
  • Design APIs without a versioning strategy
  • Expose implementation details in the API surface
  • Create breaking changes without a migration path
  • Omit rate limiting considerations

Templates

OpenAPI 3.1 Resource Endpoint (copy-paste starter)

openapi: "3.1.0"
info:
  title: Example API
  version: "1.1.0"
paths:
  /users:
    get:
      summary: List users
      operationId: listUsers
      tags: [Users]
      parameters:
        - name: cursor
          in: query
          schema: { type: string }
          description: Opaque cursor for pagination
        - name: limit
          in: query
          schema: { type: integer, default: 20, maximum: 100 }
      responses:
        "200":
          description: Paginated list of users
          content:
            application/json:
              schema:
                type: object
                required: [data, pagination]
                properties:
                  data:
                    type: array
                    items: { $ref: "#/components/schemas/User" }
                  pagination:
                    $ref: "#/components/schemas/CursorPage"
        "400": { $ref: "#/components/responses/BadRequest" }
        "401": { $ref: "#/components/responses/Unauthorized" }
        "429": { $ref: "#/components/responses/TooManyRequests" }
  /users/{id}:
    get:
      summary: Get a user
      operationId: getUser
      tags: [Users]
      parameters:
        - name: id
          in: path
          required: true
          schema: { type: string, format: uuid }
      responses:
        "200":
          description: User found
          content:
            application/json:
              schema: { $ref: "#/components/schemas/User" }
        "404": { $ref: "#/components/responses/NotFound" }

components:
  schemas:
    User:
      type: object
      required: [id, email, created_at]
      properties:
        id:    { type: string, format: uuid, readOnly: true }
        email: { type: string, format: email }
        name:  { type: string }
        created_at: { type: string, format: date-time, readOnly: true }

    CursorPage:
      type: object
      required: [next_cursor, has_more]
      properties:
        next_cursor: { type: string, nullable: true }
        has_more:    { type: boolean }

    Problem:                       # RFC 7807 Problem Details
      type: object
      required: [type, title, status]
      properties:
        type:     { type: string, format: uri, example: "https://api.example.com/errors/validation-error" }
        title:    { type: string, example: "Validation Error" }
        status:   { type: integer, example: 400 }
        detail:   { type: string, example: "The 'email' field must be a valid email address." }
        instance: { type: string, format: uri, example: "/users/req-abc123" }

  responses:
    BadRequest:
      description: Invalid request parameters
      content:
        application/problem+json:
          schema: { $ref: "#/components/schemas/Problem" }
    Unauthorized:
      description: Missing or invalid authentication
      content:
        application/problem+json:
          schema: { $ref: "#/components/schemas/Problem" }
    NotFound:
      description: Resource not found
      content:
        application/problem+json:
          schema: { $ref: "#/components/schemas/Problem" }
    TooManyRequests:
      description: Rate limit exceeded
      headers:
        Retry-After: { schema: { type: integer } }
      content:
        application/problem+json:
          schema: { $ref: "#/components/schemas/Problem" }

  securitySchemes:
    BearerAuth:
      type: http
      scheme: bearer
      bearerFormat: JWT

security:
  - BearerAuth: []

RFC 7807 Error Response (copy-paste)

{
  "type": "https://api.example.com/errors/validation-error",
  "title": "Validation Error",
  "status": 422,
  "detail": "The 'email' field must be a valid email address.",
  "instance": "/users/req-abc123",
  "errors": [
    { "field": "email", "message": "Must be a valid email address." }
  ]
}
  • Always use Content-Type: application/problem+json for error responses.
  • type must be a stable, documented URI — never a generic string.
  • detail must be human-readable and actionable.
  • Extend with errors[] for field-level validation failures.

Output Checklist

When delivering an API design, provide:

  1. Resource model and relationships (diagram or table)
  2. Endpoint specifications with URIs and HTTP methods
  3. OpenAPI 3.1 specification (YAML)
  4. Authentication and authorization flows
  5. Error response catalog (all 4xx/5xx with type URIs)
  6. Pagination and filtering patterns
  7. Versioning and deprecation strategy
  8. Validation result: npx @redocly/cli lint openapi.yaml passes with no errors

Knowledge Reference

REST architecture, OpenAPI 3.1, GraphQL, HTTP semantics, JSON:API, HATEOAS, OAuth 2.0, JWT, RFC 7807 Problem Details, API versioning patterns, pagination strategies, rate limiting, webhook design, SDK generation

Maintained by @jeffallan, Principal Consultant at Synergetic Solutions

Documentation

FAQ

What does the api-designer skill do?

Use when designing REST or GraphQL APIs, creating OpenAPI specifications, or planning API architecture. Invoke for resource modeling, versioning strategies, pagination patterns, error handling standards.

How do I install api-designer?

Run npx skills add https://github.com/jeffallan/claude-skills --skill api-designer in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/api-designer/ (personal) or .claude/skills/api-designer/ (project).

Which AI agents can use api-designer?

Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.

Is api-designer safe to install?

Security partners have reviewed it: Gen Agent Trust Hub flagged risks; Socket passed; Snyk flagged items to review; Runlayer passed; ZeroLeaks passed. As with any skill, read the SKILL.md and bundled scripts before installing.

Who maintains api-designer?

It is published by jeffallan in jeffallan/claude-skills. It has 6,531 recorded installs.

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