Api Designer

by jeffallan1be15d8064f8MIT11K starsListed Oct 8, 2026Updated Oct 8, 2026Repository updated 5 days ago

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.

Instructions onlySoftware Development

AI-generated overview

Guides REST and GraphQL API design, producing OpenAPI 3.1 specifications with versioning, pagination and error standards.

What it does: This skill acts as an API architect that walks through domain analysis, resource modeling, endpoint design, contract specification, mock verification and evolution planning. It produces OpenAPI 3.1 YAML specifications, resource models, endpoint definitions, authentication flows, error response catalogs and pagination and versioning strategies. It also supplies copy-paste templates for OpenAPI endpoints and RFC 7807 problem-detail error responses, plus reference material on REST patterns, versioning, pagination, error handling and OpenAPI.
When to use it: Use it when designing REST or GraphQL APIs, creating OpenAPI specifications, or planning API architecture. It fits resource modeling, versioning strategies, pagination patterns and error handling standards work.
Requirements: Instructions only; no scripts are shipped. The workflow references optional external tooling run via npx: @redocly/cli for linting and @stoplight/prism-cli for mock servers, which require Node.js and network access to fetch packages.

API Designer

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

Core Workflow

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

Reference Guide

Load detailed guidance based on context:

Topic	Reference	Load When
REST Patterns	`references/rest-patterns.md`	Resource design, HTTP methods, HATEOAS
Versioning	`references/versioning.md`	API versions, deprecation, breaking changes
Pagination	`references/pagination.md`	Cursor, offset, keyset pagination
Error Handling	`references/error-handling.md`	Error responses, RFC 7807, status codes
OpenAPI	`references/openapi.md`	OpenAPI 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)

yaml

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: []

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)

json

{  "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." }  ]}

{  "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:

Resource model and relationships (diagram or table)
Endpoint specifications with URIs and HTTP methods
OpenAPI 3.1 specification (YAML)
Authentication and authorization flows
Error response catalog (all 4xx/5xx with type URIs)
Pagination and filtering patterns
Versioning and deprecation strategy
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

Source and attribution

Source:jeffallan/claude-skillsinskills/api-designerat commit1be15d8

License: MIT

Content belongs to its original authors. SourceWeft indexes it from a public repository.

Report or request removal

Api Designer

API Designer

Core Workflow

Reference Guide

Constraints

MUST DO

MUST NOT DO

Templates

OpenAPI 3.1 Resource Endpoint (copy-paste starter)

RFC 7807 Error Response (copy-paste)

Output Checklist

Knowledge Reference

Source and attribution

More from jeffallan/claude-skills

Wordpress Pro

Vue Expert Js

The Fool

Swift Expert

Sql Pro

Spring Boot Engineer

More in Software Development

Playground

M5 Onboard

Cardputer Buddy

Dpop Adoption

Gemini Live Api

Gemini Api