Agent skill

API Design

by aiskillstore in aiskillstore/marketplace

Design RESTful and GraphQL APIs following best practices. An agent skill from aiskillstore/marketplace.

Apache-2.0Auto-check passedBackend & APIs

Install API Design

skills CLI
$ npx skills add aiskillstore/marketplace --skill api-design -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install aiskillstore/marketplace api-design --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/aiskillstore/marketplace.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/supercent-io/api-design .claude/skills/api-design && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
api-design
GitHub stars
430
Used in
1 other repo
Token cost
~1.8k tokens
SKILL.md length
324 words
Files
3
Skills in repo
1,108
Repo updated
First seen
Licence
Apache-2.0

At a glance

Design RESTful and GraphQL APIs following best practices. An agent skill from aiskillstore/marketplace.

  • Works in 8 steps: Define API requirements → Design REST API → Request/Response format → …
  • Creating new APIs
  • SKILL.md covers When to use this skill, Instructions, Best practices and Common patterns, plus 3 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

API Design is an agent skill from aiskillstore/marketplace. Design RESTful and GraphQL APIs following best practices. Use when creating new APIs, refactoring existing endpoints, or documenting API specifications. Handles OpenAPI, REST, GraphQL, versioning.

Its SKILL.md is about 1.8k tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files (for example `skill-report.json`).

It sits in Backend & APIs, covering GraphQL, OpenAPI specifications and API design. It works with GraphQL and OpenAPI. The repository describes itself as: Security-audited skills for Claude, Codex & Claude Code. One-click install, quality verified. The licence is Apache-2.0.

When your agent uses it

  • Creating new APIs
  • Refactoring existing endpoints
  • Documenting API specifications

Example prompts

  • “/api-design”

Workflow steps

8 steps, taken from the step headings in SKILL.md.

  1. Define API requirements
  2. Design REST API
  3. Request/Response format
  4. Error handling
  5. Pagination
  6. Authentication
  7. Versioning
  8. Documentation

What it can do on your machine

Read from SKILL.md and the folder at commit ad8daf7. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are json, yaml and graphql).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • swagger.io
    • restfulapi.net
    • graphql.org
    • httpstatuses.com

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

API Design loads about 1.8k tokens when it runs. Until then it costs about 52 tokens; SKILL.md has 324 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~52
When it runs · the whole SKILL.md, loaded when a task matches
~1.8k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from aiskillstore/marketplace at commit ad8daf7, republished under its Apache-2.0 licence (© aiskillstore). 324 words, ~1,799 tokens.

Download SKILL.mdSave it as .claude/skills/api-design/SKILL.md (or your agent's skills folder). This skill also uses 2 other files; get the full folder from GitHub.
name
api-design
description
Design RESTful and GraphQL APIs following best practices. Use when creating new APIs, refactoring existing endpoints, or documenting API specifications. Handles OpenAPI, REST, GraphQL, versioning.
license
Apache-2.0
metadata.version
1.0.0
metadata.author
Agent Skills Team
metadata.tags
api-design, REST, GraphQL, OpenAPI, versioning, backend
metadata.platforms
Claude, ChatGPT, Gemini

API Design

When to use this skill

  • Designing new REST APIs
  • Creating GraphQL schemas
  • Refactoring API endpoints
  • Documenting API specifications
  • API versioning strategies
  • Defining data models and relationships

Instructions

Step 1: Define API requirements
  • Identify resources and entities
  • Define relationships between entities
  • Specify operations (CRUD, custom actions)
  • Plan authentication/authorization
  • Consider pagination, filtering, sorting
Step 2: Design REST API

Resource naming:

  • Use nouns, not verbs: /users not /getUsers
  • Use plural names: /users/{id}
  • Nest resources logically: /users/{id}/posts
  • Keep URLs short and intuitive

HTTP methods:

  • GET: Retrieve resources (idempotent)
  • POST: Create new resources
  • PUT: Replace entire resource
  • PATCH: Partial update
  • DELETE: Remove resources (idempotent)

Response codes:

  • 200 OK: Success with response body
  • 201 Created: Resource created successfully
  • 204 No Content: Success with no response body
  • 400 Bad Request: Invalid input
  • 401 Unauthorized: Authentication required
  • 403 Forbidden: No permission
  • 404 Not Found: Resource doesn't exist
  • 409 Conflict: Resource conflict
  • 422 Unprocessable Entity: Validation failed
  • 500 Internal Server Error: Server error

Example REST endpoint:

GET    /api/v1/users           # List users
GET    /api/v1/users/{id}      # Get user
POST   /api/v1/users           # Create user
PUT    /api/v1/users/{id}      # Update user
PATCH  /api/v1/users/{id}      # Partial update
DELETE /api/v1/users/{id}      # Delete user
Step 3: Request/Response format

Request example:

json
POST /api/v1/users
Content-Type: application/json

{
  "name": "John Doe",
  "email": "john@example.com",
  "role": "admin"
}

Response example:

json
HTTP/1.1 201 Created
Content-Type: application/json
Location: /api/v1/users/123

{
  "id": 123,
  "name": "John Doe",
  "email": "john@example.com",
  "role": "admin",
  "created_at": "2024-01-15T10:30:00Z",
  "updated_at": "2024-01-15T10:30:00Z"
}
Step 4: Error handling

Error response format:

json
{
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid input provided",
    "details": [
      {
        "field": "email",
        "message": "Invalid email format"
      }
    ]
  }
}
Step 5: Pagination

Query parameters:

GET /api/v1/users?page=2&limit=20&sort=-created_at&filter=role:admin

Response with pagination:

json
{
  "data": [...],
  "pagination": {
    "page": 2,
    "limit": 20,
    "total": 100,
    "pages": 5
  },
  "links": {
    "self": "/api/v1/users?page=2&limit=20",
    "first": "/api/v1/users?page=1&limit=20",
    "prev": "/api/v1/users?page=1&limit=20",
    "next": "/api/v1/users?page=3&limit=20",
    "last": "/api/v1/users?page=5&limit=20"
  }
}
Step 6: Authentication

Options:

  • JWT (JSON Web Tokens)
  • OAuth 2.0
  • API Keys
  • Session-based

Example with JWT:

GET /api/v1/users
Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
Step 7: Versioning

URL versioning (recommended):

/api/v1/users
/api/v2/users

Header versioning:

GET /api/users
Accept: application/vnd.api+json; version=1
Step 8: Documentation

Create OpenAPI 3.0 specification:

yaml
openapi: 3.0.0
info:
  title: User Management API
  version: 1.0.0
  description: API for managing users
servers:
  - url: https://api.example.com/v1
paths:
  /users:
    get:
      summary: List users
      parameters:
        - name: page
          in: query
          schema:
            type: integer
            default: 1
        - name: limit
          in: query
          schema:
            type: integer
            default: 20
      responses:
        '200':
          description: Successful response
          content:
            application/json:
              schema:
                type: object
                properties:
                  data:
                    type: array
                    items:
                      $ref: '#/components/schemas/User'
    post:
      summary: Create user
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/UserCreate'
      responses:
        '201':
          description: User created
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/User'
components:
  schemas:
    User:
      type: object
      properties:
        id:
          type: integer
        name:
          type: string
        email:
          type: string
          format: email
        created_at:
          type: string
          format: date-time
    UserCreate:
      type: object
      required:
        - name
        - email
      properties:
        name:
          type: string
        email:
          type: string
          format: email

Best practices

  1. Consistency: Use consistent naming, structure, and patterns
  2. Versioning: Always version your APIs from the start
  3. Security: Implement authentication and authorization
  4. Validation: Validate all inputs on the server side
  5. Rate limiting: Protect against abuse
  6. Caching: Use ETags and Cache-Control headers
  7. CORS: Configure properly for web clients
  8. Documentation: Keep docs up-to-date with code
  9. Testing: Test all endpoints thoroughly
  10. Monitoring: Log requests and track performance

Common patterns

Filtering:

GET /api/v1/users?role=admin&status=active

Sorting:

GET /api/v1/users?sort=-created_at,name

Field selection:

GET /api/v1/users?fields=id,name,email

Batch operations:

POST /api/v1/users/batch
{
  "operations": [
    {"action": "create", "data": {...}},
    {"action": "update", "id": 123, "data": {...}}
  ]
}

GraphQL alternative

If REST doesn't fit, consider GraphQL:

graphql
type User {
  id: ID!
  name: String!
  email: String!
  posts: [Post!]!
  createdAt: DateTime!
}

type Query {
  users(page: Int, limit: Int): [User!]!
  user(id: ID!): User
}

type Mutation {
  createUser(input: CreateUserInput!): User!
  updateUser(id: ID!, input: UpdateUserInput!): User!
  deleteUser(id: ID!): Boolean!
}

References

Examples

Example 1: Basic usage
<!-- Add example content here -->
Example 2: Advanced usage
<!-- Add advanced example content here -->

© aiskillstore, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 2 other files in skills/supercent-io/api-design of aiskillstore/marketplace.

  • SKILL.md
  • SKILL.toon
  • skill-report.json

Open the folder on GitHubat commit ad8daf7

Used in 1 other repository

We found 1 copy of this SKILL.md (exact, near-identical or edited) in other folders, from 1 other GitHub owner. This page covers the copy in aiskillstore/marketplace, which our catalogue first saw on October 7, 2026.

Compare with similar skills

API Design next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

API Design compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
API Design this skillaiskillstore/marketplace4301 repos~1.8kAutomated safety check: PassApache-2.0
API DesignerJeffallan/claude-skills12k2 repos~2kAutomated safety check: PassMIT
API Contract Designrsmdt/the-startup551—~1.1kAutomated safety check: PassMIT
API Architectcuriositech/some_claude_skills2431 repos~1.4kAutomated safety check: PassMIT
API Designermajiayu000/claude-skill-registry6661 repos~3.5kAutomated safety check: PassMIT
Graphos Factoryapollographql/skills117—~15kAutomated safety check: PassMIT

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Works with

Categories

Questions about API Design

What does API Design do?

Design RESTful and GraphQL APIs following best practices. An agent skill from aiskillstore/marketplace. API Design is an agent skill from aiskillstore/marketplace. Design RESTful and GraphQL APIs following best practices.

When should I use API Design?

API Design fits situations like: creating new APIs; refactoring existing endpoints; documenting API specifications.

How do I install API Design in Claude Code?

Run `npx skills add aiskillstore/marketplace --skill api-design -a claude-code`. Or copy the skill folder (skills/supercent-io/api-design in aiskillstore/marketplace) into .claude/skills/api-design in your project. Claude Code loads it when a task matches its description.

How do I install API Design in Codex?

Run `npx skills add aiskillstore/marketplace --skill api-design -a codex`. Or copy the skill folder (skills/supercent-io/api-design in aiskillstore/marketplace) into .agents/skills/api-design in your project. Codex loads it when a task matches its description.

Can I use API Design in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add aiskillstore/marketplace --skill api-design -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/api-design, .gemini/skills/api-design, .github/skills/api-design and .opencode/skills/api-design in your project.

What does API Design need to run?

SKILL.md names no scripts, command-line tools or credentials: API Design is instructions for the agent only.

Does API Design access the network?

SKILL.md names 4 domains. As links in the text: swagger.io, restfulapi.net, graphql.org and httpstatuses.com. This is read from the text; nothing was executed.

Is API Design safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does API Design use?

API Design is published under the Apache-2.0 licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does API Design use?

About 1.8k tokens (SKILL.md is roughly 7.2k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to API Design?

Skills that share tags, products or a category with API Design: API Designer (Jeffallan/claude-skills, 12k stars), API Contract Design (rsmdt/the-startup, 551 stars), API Architect (curiositech/some_claude_skills, 243 stars) and API Designer (majiayu000/claude-skill-registry, 666 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains API Design?

aiskillstore (a GitHub organization) maintains it in aiskillstore/marketplace, which has 430 GitHub stars. The repository holds 1,108 skills in this directory. The repository was last updated on October 7, 2026.

Source: aiskillstore/marketplace on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.