openapi-design

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Contract-first REST API design with OpenAPI 3.1 specification

Design

What this skill does


# OpenAPI Design Skill

## When to Use This Skill

Use this skill when:

- **Designing REST APIs** - OpenAPI 3.1 for contract-first API design
- **Defining API contracts** - Schemas, paths, parameters, responses
- **API best practices** - Naming conventions, status codes, versioning

## MANDATORY: Documentation-First Approach

Before creating OpenAPI specifications:

1. **Invoke `docs-management` skill** for API design patterns
2. **Verify OpenAPI 3.1 syntax** via MCP servers (context7 for latest spec)
3. **Base all guidance on OpenAPI 3.1 specification**

## Contract-First Approach

### Why Contract-First?

1. **Design before implementation**: Think through API before coding
2. **Parallel development**: Frontend and backend can work simultaneously
3. **Clear contract**: Unambiguous specification for all parties
4. **Auto-generation**: Generate clients, servers, documentation
5. **Validation**: Validate requests/responses against schema

### Workflow

```text
Requirements → OpenAPI Spec → Review → Generate → Implement → Test
     ↑                                                      ↓
     ←←←←←←←←←←←←← Iterate as needed ←←←←←←←←←←←←←←←←←←←←←←
```

## OpenAPI 3.1 Structure Overview

```yaml
openapi: 3.1.0
info:
  title: API Title
  version: 1.0.0
  description: API description

servers:
  - url: https://api.example.com/v1
    description: Production

tags:
  - name: Orders
    description: Order management

paths:
  # Define endpoints - see paths-definition.md

components:
  schemas: { }
  securitySchemes: { }
  responses: { }
  parameters: { }
```

**For complete template**: See [paths-definition.md](references/paths-definition.md)

## Quick Reference

### HTTP Methods

| Method | Purpose | Idempotent |
|--------|---------|------------|
| GET | Retrieve resource(s) | Yes |
| POST | Create resource | No |
| PUT | Replace resource | Yes |
| PATCH | Partial update | No |
| DELETE | Remove resource | Yes |

### Common Status Codes

| Code | Use For |
|------|---------|
| 200 | Successful GET, PUT, PATCH |
| 201 | Resource created (POST) |
| 204 | Successful DELETE |
| 400 | Malformed request |
| 401 | Authentication required |
| 404 | Resource not found |
| 422 | Validation error |

**For complete guidance**: See [design-best-practices.md](references/design-best-practices.md)

## Design Workflow

1. **Understand requirements**: What operations are needed?
2. **Design resources**: Identify entities and relationships
3. **Define schemas**: Create reusable component schemas
4. **Specify endpoints**: Define paths and operations
5. **Add security**: Configure authentication/authorization
6. **Document examples**: Add request/response examples
7. **Validate**: Use linting tools (Spectral, etc.)
8. **Review**: Get team feedback before implementation

## References

Load on-demand based on need:

| Reference | Load When |
|-----------|-----------|
| [paths-definition.md](references/paths-definition.md) | Defining REST endpoints, operations, parameters |
| [components-definition.md](references/components-definition.md) | Creating schemas, responses, security schemes |
| [design-best-practices.md](references/design-best-practices.md) | Reviewing naming, status codes, versioning |

## Related Skills (Cross-Plugin)

| Phase | Skill | Plugin | Purpose |
| ----- | ----- | ------ | ------- |
| DESIGN | `openapi-design` (this skill) | formal-specification | Architecture research, pattern selection |
| AUTHORING | `openapi-authoring` | spec-driven-development | Concrete YAML file creation |
| GOVERNANCE | `contract-first-design` | spec-driven-development | API governance, code generation |

**Workflow:** Design (research patterns) → Author (create YAML) → Govern (enforce contracts)

## External References

- [OpenAPI 3.1 Specification](https://spec.openapis.org/oas/v3.1.0) - Official specification
- [RFC 7231 - HTTP Semantics](https://datatracker.ietf.org/doc/html/rfc7231) - HTTP methods and status codes
- [RFC 7807 - Problem Details](https://datatracker.ietf.org/doc/html/rfc7807) - Standard error response format
- [Spectral](https://stoplight.io/open-source/spectral) - OpenAPI linting tool

## MCP Research

For current OpenAPI patterns and tools:

```text
perplexity: "OpenAPI 3.1 specification" "REST API design patterns"
context7: "openapi" (for official documentation)
ref: "OpenAPI spec examples" "JSON Schema patterns"
```

## Version History

- **v2.0.0** (2026-01-17): Refactored to progressive disclosure pattern
  - Extracted 3 reference files (~500 lines)
  - Hub reduced from 698 to ~130 lines
- **v1.0.0** (2025-12-26): Initial release

---

**Last Updated:** 2026-01-17

Files: 4

Size: 19.7 KB

Complexity: 38/100

Category: Design

Source: https://github.com/melodic-software/claude-code-plugins/tree/main/plugins/formal-specification/skills/openapi-design

Related in Design

contribute

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Local-only OSS contribution command center. Auto-refreshes the user's in-flight PR and issue state on invoke so conversations start with full context — no need to brief Claude on what's in flight. Helps the user find issues to contribute to on GitHub, builds per-repo dossiers of what each upstream expects (CLA, DCO, branch convention, AI policy, draft-first, review bots, issue templates), runs deterministic gates before any external action so AI-assisted contributions don't reach maintainers as slop. State is markdown-only: candidate files at ~/.contribute-system/candidates/, repo dossiers at ~/.contribute-system/research/, append-only event log at ~/.contribute-system/log.jsonl. No database, no cloud calls. Use when the user asks about their PRs / issues / contributions, wants to find new work to take on, claim an issue, build/refresh a repo's dossier, or draft a Design Issue or PR. Trigger with "/contribute", "what's my PR status", "find a contribution", "claim issue X", "draft a Design Issue for Y", "refresh dossier for Z".

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User-triggered deep architectural analysis of a codebase or scoped subtree across eight modes — information architecture, data flow, integration points, UI surfaces, interaction patterns, data model, control flow, and failure modes. This skill should be used when the user asks to "diagram this codebase," "map the architecture," "show the data flow," "give me an ERD," "trace control flow," "find the integration points," "verify the layout pattern," "audit the UX architecture," or any similar request whose primary deliverable is mermaid diagrams plus cited reports under docs/architecture/. Dispatches haiku/sonnet sub-agents in parallel for per-mode exploration, then verifies every citation mechanically before any node lands in a diagram. Not for one-off prose explanations of code (use code-explanation) or for high-level system design from scratch (use system-design).

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Model Context Protocol (MCP) server development and tool management. Languages: Python, TypeScript. Capabilities: build MCP servers, integrate external APIs, discover/execute MCP tools, manage multi-server configs, design agent-centric tools. Actions: create, build, integrate, discover, execute, configure MCP servers/tools. Keywords: MCP, Model Context Protocol, MCP server, MCP tool, stdio transport, SSE transport, tool discovery, resource provider, prompt template, external API integration, Gemini CLI MCP, Claude MCP, agent tools, tool execution, server config. Use when: building MCP servers, integrating external APIs as MCP tools, discovering available MCP tools, executing MCP capabilities, configuring multi-server setups, designing tools for AI agents.

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Designscripts