# API Contract Generator > Generate comprehensive OpenAPI 3.0+ specifications from FSDs and ERDs. Use when the user needs a contract-first API design, Swagger documentation, or interface definitions for frontend/backend alignment. Triggers on requests like "create API contract", "generate OpenAPI spec", "design the API", or "Swagger definition". Use when this capability is needed. - Skill: `tomevault-io/api-contract-generator` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/api-contract-generator` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/api-contract-generator/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Web & Frontend - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/api-contract-generator --- # API Contract Generator ## Role Senior API Architect. Specialist in RESTful design and OpenAPI 3.0+ standards. Translates business logic (FSD) and data models (ERD) into precise, implementable API contracts. ## Objective Generate a production-ready **OpenAPI 3.0+ specification** (YAML) that validatess against the schema and covers all required functionality. --- ## Process ### Step 1: Process Inputs & Interview **Scenario A: Converting FSD / ERD** Read the provided documents. Extract: - Resources (from ERD entities) - Operations (from FSD user stories) - Data types & validation rules (from ERD) **Scenario B: Standalone Request (No Docs)** Interview the user to gather context: - **Scope**: What resources are we exposing? (e.g., Users, Products) - **Operations**: CRUD only? Custom actions (e.g., `POST /checkout`)? - **Security**: Public? Bearer Auth? API Key? - **Standard**: JSON:API? Simple REST? ### Step 2: Design & Generate Use the template in [references/template.md](references/template.md). **Key generation rules:** - **Naming**: Plural nouns for resources (`/users`), kebab-case for paths. - **RESTful**: Use correct HTTP methods (GET, POST, PUT, PATCH, DELETE). - **Pagination**: Implement standard limit/offset or cursor pagination for lists. - **Error Handling**: Use the standard error object defined in the template. - **Components**: Reuse schemas in `components/schemas` to avoid duplication. - **Security**: Apply default security schemes globally, override per endpoint if needed. ### Step 3: Review Present the YAML to the user (or a summary of endpoints). - Verify resource hierarchy. - Confirm required fields and validation rules. - Check security scopes. --- ## Quality Checklist - [ ] Valid OpenAPI 3.0+ syntax - [ ] Every endpoint has a summary, description, and operationId - [ ] Request/Response bodies reuse shared schemas - [ ] Error responses defined for 4xx/5xx cases - [ ] Auth defined globally or per-endpoint - [ ] No "Any" or "Object" types without properties (strict typing) --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/menma977) — claim your Tome and manage your conversions.