api-designer
REST and GraphQL API architect for designing robust, scalable APIs. Use when designing new APIs or improving existing ones.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/zhaono1/agent-playbook --skill api-designer- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads api-designer automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
API Designer
Expert in designing REST and GraphQL APIs that are robust, scalable, and maintainable.
When This Skill Activates
Activates when you:
- Design a new API
- Review API design
- Improve existing API
- Create API specifications
REST API Design Principles
1. Resource-Oriented Design
Good:
GET /users # List users
POST /users # Create user
GET /users/{id} # Get specific user
PATCH /users/{id} # Update user
DELETE /users/{id} # Delete user
Avoid:
POST /getUsers # Should be GET
POST /users/create # Redundant
GET /users/get/{id} # Redundant
2. HTTP Methods
| Method | Safe | Idempotent | Purpose |
|---|---|---|---|
| GET | ✓ | ✓ | Read resource |
| POST | ✗ | ✗ | Create resource |
| PUT | ✗ | ✓ | Replace resource |
| PATCH | ✗ | ✗ | Update resource |
| DELETE | ✗ | ✓ | Delete resource |
3. Status Codes
| Code | Meaning | Usage |
|---|---|---|
| 200 | OK | Successful GET, PATCH, DELETE |
| 201 | Created | Successful POST |
| 204 | No Content | Successful DELETE with no body |
| 400 | Bad Request | Invalid input |
| 401 | Unauthorized | Missing or invalid auth |
| 403 | Forbidden | Authenticated but not authorized |
| 404 | Not Found | Resource doesn't exist |
| 409 | Conflict | Resource already exists |
| 422 | Unprocessable | Valid syntax but semantic errors |
| 429 | Too Many Requests | Rate limit exceeded |
| 500 | Internal Server Error | Server error |
4. Naming Conventions
- URLs: kebab-case (
/user-preferences) - JSON: camelCase (
{"userId": "123"}) - Query params: snake_case or camelCase (
?page_size=10)
5. Pagination
GET /users?page=1&page_size=20
Response:
{
"data": [...],
"pagination": {
"page": 1,
"page_size": 20,
"total": 100,
"total_pages": 5
}
}
6. Filtering and Sorting
GET /users?status=active&sort=-created_at,name
# -created_at = descending
# name = ascending
GraphQL API Design
Schema Design
type Query {
user(id: ID!): User
users(limit: Int, offset: Int): UserConnection!
}
type Mutation {
createUser(input: CreateUserInput!): CreateUserPayload!
updateUser(id: ID!, input: UpdateUserInput!): UpdateUserPayload!
}
type User {
id: ID!
email: String!
profile: Profile
posts(first: Int, after: String): PostConnection!
}
type UserConnection {
edges: [UserEdge!]!
pageInfo: PageInfo!
}
type UserEdge {
node: User!
cursor: String!
}
type PageInfo {
hasNextPage: Boolean!
hasPreviousPage: Boolean!
startCursor: String
endCursor: String
}
Best Practices
- Nullability: Default to non-null, nullable only when appropriate
- Connections: Use cursor-based pagination for lists
- Payloads: Use mutation payloads for consistent error handling
- Descriptions: Document all types and fields
API Versioning
Approaches
URL Versioning (Recommended):
/api/v1/users
/api/v2/users
Header Versioning:
GET /users
Accept: application/vnd.myapi.v2+json
Versioning Guidelines
- Start with v1
- Maintain backwards compatibility when possible
- Deprecate old versions with notice
- Document breaking changes
Authentication & Authorization
Authentication Methods
- JWT Bearer Token
Authorization: Bearer <token>
- API Key
X-API-Key: <key>
- OAuth 2.0
Authorization: Bearer <access_token>
Authorization
- Use roles/permissions
- Document required permissions per endpoint
- Return 403 for authorization failures
Rate Limiting
HTTP/1.1 200 OK
X-RateLimit-Limit: 1000
X-RateLimit-Remaining: 999
X-RateLimit-Reset: 1631234567
Recommended limits:
- Public APIs: 100-1000 requests/hour
- Authenticated APIs: 1000-10000 requests/hour
- Webhooks: 10-100 requests/minute
Documentation Requirements
- All endpoints documented
- Request/response examples
- Authentication requirements
- Error response formats
- Rate limits
- SDK examples (if available)
Scripts
Generate API scaffold:
python3 scripts/generate_api.py --name <resource-name> --output api-design.md
Validate API design:
python3 scripts/validate_api.py --input api-design.md
References
references/rest-patterns.md- REST design patternsreferences/graphql-patterns.md- GraphQL design patterns- REST API Tutorial
- GraphQL Best Practices
FAQ
What does the api-designer skill do?
REST and GraphQL API architect for designing robust, scalable APIs. Use when designing new APIs or improving existing ones.
How do I install api-designer?
Run npx skills add https://github.com/zhaono1/agent-playbook --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?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains api-designer?
It is published by zhaono1 in zhaono1/agent-playbook. It has 699 recorded installs.
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