api-contract

name	api-contract
description	Configure this skill should be used when the user asks about "API contract", "api-contract.md", "shared interface", "TypeScript interfaces", "request response schemas", "endpoint design", or needs guidance on designing contracts that coordinate backend and frontend agents. Use when building or modifying API endpoints. Trigger with phrases like 'create API', 'design endpoint', or 'API scaffold'.
allowed-tools	Read
version	1.20.0
author	Damien Laine <[e-mail]>
license	MIT
tags	["community","api","typescript"]
compatibility	Designed for Claude Code, also compatible with Codex and OpenClaw

API Contract

Overview

API Contract guides the creation of api-contract.md files that serve as the shared interface between backend and frontend agents during sprint execution. The contract defines request/response schemas, endpoint routes, TypeScript interfaces, and error formats so that implementation agents build to an agreed specification without direct coordination.

Prerequisites

• Sprint directory initialized at .claude/sprint/[N]/
• specs.md with defined feature scope and endpoint requirements
• Familiarity with RESTful API conventions (HTTP methods, status codes, JSON schemas)
• TypeScript knowledge for interface definitions (recommended)

Instructions

1. Create api-contract.md in the sprint directory (.claude/sprint/[N]/api-contract.md). Define each endpoint using the standard format: HTTP method, route path, description, request body, response body with status code, and error codes. See ${CLAUDE_SKILL_DIR}/references/writing-endpoints.md for the full template.
2. Define TypeScript interfaces for all request and response types. Use explicit types instead of any, mark optional fields with ?, and use string | null for nullable values. Reference ${CLAUDE_SKILL_DIR}/references/typescript-interfaces.md for canonical type patterns.
3. For list endpoints, include pagination parameters and the PaginatedResponse<T> wrapper. Standardize on page, limit, sort, and order query parameters as documented in ${CLAUDE_SKILL_DIR}/references/pagination.md.
4. Document all response states: success (200, 201, 204), client errors (400, 401, 403, 404, 422), and empty states. Use a consistent error response format with code, message, and optional details fields.
5. Follow best practices from ${CLAUDE_SKILL_DIR}/references/best-practices.md: be specific about field constraints (e.g., "string, required, valid email format"), include request/response examples, reference shared types instead of duplicating, and omit implementation details (no database columns, framework names, or file paths).
6. Share the contract file path in SPAWN REQUEST blocks so both backend and frontend agents read the same interface definition.

Output

• api-contract.md containing all endpoint definitions with typed request/response schemas