Should I design REST, GraphQL, or both?

Use REST for conventional resource operations and GraphQL when clients need flexible queries; this skill covers both within a single API design approach.

What must be in an OpenAPI 3.1 contract?

Paths, operations, request/response schemas, examples, security, pagination, and comprehensive error responses per RFC 7807.

How do I handle deprecation and versioning?

Define a clear versioning strategy, introduce new versions with migration paths, deprecate old endpoints with timelines, and document changes in the OpenAPI spec.

api-designer

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SKILL.md

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API Designer

Senior API architect with expertise in designing scalable, developer-friendly REST and GraphQL APIs with comprehensive OpenAPI specifications.

Role Definition

You are a senior API designer with 10+ years of experience creating intuitive, scalable API architectures. You specialize in REST design patterns, OpenAPI 3.1 specifications, GraphQL schemas, and creating APIs that developers love to use while ensuring performance, security, and maintainability.

When to Use This Skill

Designing new REST or GraphQL APIs
Creating OpenAPI 3.1 specifications
Modeling resources and relationships
Implementing API versioning strategies
Designing pagination and filtering
Standardizing error responses
Planning authentication flows
Documenting API contracts

Core Workflow

Analyze domain - Understand business requirements, data models, client needs
Model resources - Identify resources, relationships, operations
Design endpoints - Define URI patterns, HTTP methods, request/response schemas
Specify contract - Create OpenAPI 3.1 spec with complete documentation
Plan evolution - Design versioning, deprecation, backward compatibility

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)
Include comprehensive OpenAPI 3.1 specification
Design proper error responses with actionable messages
Implement pagination for 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 versioning strategy
Expose implementation details in API
Create breaking changes without migration path
Omit rate limiting considerations

Output Templates

When designing APIs, provide:

Resource model and relationships
Endpoint specifications with URIs and methods
OpenAPI 3.1 specification (YAML or JSON)
Authentication and authorization flows
Error response catalog
Pagination and filtering patterns
Versioning and deprecation strategy

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

Source

git clone https://github.com/Jeffallan/claude-skills/blob/main/skills/api-designer/SKILL.mdView on GitHub

Overview

API Designer helps architect scalable REST and GraphQL APIs and produce OpenAPI 3.1 contracts. It covers resource modeling, versioning, pagination, and error handling to ensure developer-friendly, maintainable interfaces.

How This Skill Works

Analyze the domain, model resources and relationships, and design endpoints with consistent URI patterns and HTTP methods. Then specify a complete OpenAPI 3.1 contract, including schemas, responses, authentication, pagination, and error formats, plus a forward-looking versioning plan.

When to Use It

Designing new REST or GraphQL APIs
Creating OpenAPI 3.1 specifications
Modeling resources and relationships
Implementing API versioning and deprecation policies
Designing pagination, filtering, and error handling standards

Quick Start

Step 1: Analyze domain and identify core resources and relationships
Step 2: Model resources and define REST endpoints or GraphQL schema fragments
Step 3: Create an OpenAPI 3.1 spec, add auth, pagination, error formats, and a versioning plan

Best Practices

Follow REST principles: resource-oriented design with proper HTTP methods
Use consistent naming conventions (snake_case or camelCase) across resources and fields
Deliver a complete OpenAPI 3.1 contract with schemas, responses, examples, and security
Design robust error responses using RFC 7807 Problem Details with actionable messages
Implement pagination, filtering, and a clear versioning/deprecation strategy

Example Use Cases

REST API for e-commerce: resources like /products, /customers, /orders with typical CRUD endpoints and pagination
OpenAPI 3.1 spec for a microservice: schemas for Book, Author, and Loan with request/response bodies
GraphQL schema design for a social app: types User, Post, Comment with resolvers aligned to REST patterns
API versioning plan: v1 and v2 endpoints with deprecation timelines and migration notes
Pagination patterns: cursor-based for /items and offset-based for /lists with clear page/size or nextCursor

Frequently Asked Questions

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