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Api Designer Guide: Usage, Examples, and Best Practices for Beginners

Cowrie
Cowrie
Dev @ Bswen

Purpose

This post demonstrates how to use the Api Designer skill in Claude Code to design REST APIs with proper architecture patterns.

Environment

  • Claude Code with claude-skills plugin
  • Target audience: Beginner to intermediate developers
  • Focus: REST API design and architecture

What is Api Designer?

When I need to design REST APIs, I used to struggle with:

  • Resource naming conventions
  • HTTP method selection
  • Status code decisions
  • Response structure design

The Api Designer skill in Claude Code helps solve these problems by providing structured API design guidance. It’s part of the claude-skills ecosystem - a collection of specialized skills that extend Claude Code’s capabilities.

When to Use Api Designer

I use this skill when:

  • Starting a new API project
  • Adding endpoints to existing APIs
  • Refactoring API structure
  • Documenting API contracts
  • Reviewing API design decisions

The key benefit is consistency - my APIs follow industry standards without me having to remember every rule.

Installation and Setup

First, I need to install claude-skills plugin:

Terminal window
# Install claude-skills
npm install -g claude-skills

Then verify the installation:

Terminal window
# Check available skills
claude-skills list


# I should see "api-designer" in the output

Core Usage Patterns

The Api Designer skill activates through specific triggers. Here are common ways I invoke it:

Direct invocation:

Use api-designer skill to create endpoints for a user management system

Scenario-based:

I'm building a blog API with posts, comments, and tags. Help me design the REST endpoints.

Specific questions:

What HTTP method should I use for updating a user's email address?

Practical Example: Building a Task Management API

Let me show you how I used api-designer to build a task management API.

Initial Request

I started with this prompt:

Use api-designer to design REST API for task management

The skill guided me through:

Resource Identification:

┌──────────────┐    ┌──────────────┐    ┌──────────────┐
│    Tasks     │    │   Projects   │    │     Tags     │
└──────────────┘    └──────────────┘    └──────────────┘
       │                   │                   │
       └───────────────────┴───────────────────┘
                            │
                      ┌──────────────┐
                      │ Assignments │
                      └──────────────┘

Endpoint Design:

The skill suggested these core endpoints:

GET    /api/tasks              - List all tasks
GET    /api/tasks/{id}         - Get specific task
POST   /api/tasks              - Create new task
PUT    /api/tasks/{id}         - Update task entirely
PATCH  /api/tasks/{id}         - Partial task update
DELETE /api/tasks/{id}         - Delete task


GET    /api/projects/{id}/tasks - Get tasks by project
GET    /api/tasks?tag=urgent    - Filter tasks by tag

Response Structure

The skill recommended this response format:

{
  "data": {
    "id": "task_123",
    "type": "task",
    "attributes": {
      "title": "Fix login bug",
      "description": "Users cannot login with SAML",
      "status": "in_progress",
      "priority": "high",
      "dueDate": "2026-02-20T00:00:00Z",
      "createdAt": "2026-02-14T10:30:00Z",
      "updatedAt": "2026-02-14T11:40:00Z"
    },
    "relationships": {
      "project": {
        "data": { "id": "proj_456", "type": "project" }
      },
      "assignee": {
        "data": { "id": "user_789", "type": "user" }
      },
      "tags": {
        "data": [
          { "id": "tag_1", "type": "tag" },
          { "id": "tag_2", "type": "tag" }
        ]
      }
    }
  },
  "meta": {
    "total": 1,
    "page": 1,
    "limit": 20
  }
}

Error Handling

When I asked about error responses, the skill suggested:

{
  "errors": [
    {
      "id": "error_123",
      "status": 404,
      "code": "NOT_FOUND",
      "title": "Task not found",
      "detail": "The requested task does not exist or you don't have access.",
      "meta": {
        "requestId": "req_abc123",
        "timestamp": "2026-02-14T11:40:00Z"
      }
    }
  ]
}

Common Patterns I Use

Pattern 1: Nested Resources

When I have related resources:

GET /api/projects/{id}/tasks
POST /api/projects/{id}/tasks

The skill taught me to keep nesting to 2-3 levels max:

✓ Good:  GET /api/projects/{id}/tasks/{taskId}/comments
✗ Bad:   GET /api/projects/{id}/tasks/{taskId}/comments/{commentId}/replies/{replyId}

Pattern 2: Filtering and Pagination

For list endpoints, the skill recommended:

GET /api/tasks?status=in_progress&priority=high&page=1&limit=20&sort=dueDate:asc

Pattern 3: Versioning

When APIs evolve:

/api/v1/tasks
/api/v2/tasks

The skill advised:

  • Use URL path versioning
  • Support at least 2 previous versions
  • Document deprecation timeline

Best Practices

DO

  • Use nouns for resources: /tasks not /getTasks
  • Use plural nouns: /users not /user
  • Use kebab-case: /user-preferences not /userPreferences
  • Return proper status codes: 200, 201, 204, 400, 401, 403, 404, 500
  • Include pagination metadata: total, page, limit
  • Use consistent response structure: data, errors, meta
  • Document with OpenAPI/Swagger: Machine-readable API specs
  • Use HTTP verbs correctly: GET (read), POST (create), PUT/PATCH (update), DELETE (delete)

DON’T

  • Don’t use verbs in endpoints: /getTask or /createTask
  • Don’t return plain text errors: Always JSON error objects
  • Don’t nest too deep: Max 2-3 levels
  • Don’t ignore HTTP methods: Use PUT vs PATCH correctly
  • Don’t forget idempotency: GET, PUT, DELETE should be idempotent
  • Don’t leak implementation details: /api/database/users or /api/classes/User
  • Don’t use camelCase in URLs: /api/userPreferences not /api/userPreferences

The Api Designer works well with other claude-skills:

  • springboot-patterns: If building APIs with Spring Boot
  • backend-patterns: For general backend architecture
  • security-review: To validate API security
  • code-review: To review implementation quality

Troubleshooting

When I first used api-designer, I ran into issues:

Problem: Skill not activating

Terminal window
# I checked skill installation
claude-skills list | grep api-designer


# Empty output - skill not found

Solution: I needed to reinstall claude-skills:

Terminal window
npm uninstall -g claude-skills
npm install -g claude-skills

Problem: Vague responses

  • My prompt: “Help me with APIs”
  • Skill response: Generic advice

Solution: Be specific about context:

Use api-designer to design REST endpoints for an e-commerce inventory system
with products, categories, and stock management

Summary

In this post, I showed how to use the Api Designer skill in Claude Code to design REST APIs with proper architecture. The key point is that this skill provides consistent, industry-standard API design patterns that help avoid common mistakes.

The skill helped me design:

  • Proper endpoint structures
  • Consistent response formats
  • Error handling patterns
  • Resource relationships

When I combine api-designer with other claude-skills like springboot-patterns and security-review, I get a complete API development workflow from design to implementation.

Final Words + More Resources

My intention with this article was to help others share my knowledge and experience. If you want to contact me, you can contact by email: Email me

Here are also the most important links from this article along with some further resources that will help you in this scope:

Oh, and if you found these resources useful, don’t forget to support me by starring the repo on GitHub!

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