API Contract Tester vs BBC Consumer Contracts

API Contract Tester is a web tool for checking whether frontend and backend APIs follow the same contract. It compares an expected TypeScript, OpenAPI, or JSON schema with actual API responses and identifies missing fields, extra fields, incompatible types, and null violations. Validation covers nested objects, arrays, enums, and optional fields, with mismatch reports that include suggested fixes. You can paste a schema and response into the online interface or run the tool locally as an MCP server. Installation uses `npx @clinetools/contract-test` and requires Node.js 18 or newer. The first CLI run asks about contract strictness and fields to ignore. Setup instructions support Cline and Claude Code, and contract checks can run in deployment pipelines before a frontend release. The free plan costs nothing, billed forever, and includes 100 executions per month; premium modules are excluded. Individual Dev costs $19 a month.

BBC Consumer Contracts is a free JavaScript package for executable consumer-driven API contracts. It describes the requests a consumer makes and the responses expected in return. Every contract requires consumer, name, request, and response properties. The package uses the request HTTP client and Joi schemas to check response status codes, headers, and JSON bodies. Optional before and after functions support setup and cleanup, using callbacks or asynchronous functions. Retry behavior accepts numeric or custom settings; the documented default maximum is zero. The consumer-contracts run command validates contracts recursively in a contracts directory or runs one named file. Programmatic callers can pass an array to validateContracts, which runs every contract instead of stopping at the first failure. Installation instructions cover global CLI use and local pnpm development dependencies. It requires Node.js 18 or later and pnpm 10 or later, and supports API and self-hosted use under Apache License 2.0.