API Contract Tester vs BitDive

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.

BitDive is a freemium API, web, and self-hosted tool for Java and Kotlin teams that want to verify code changes against recorded service behavior. Its agent captures method calls, SQL queries, HTTP requests, Kafka messages, JVM metrics, and exception traces, then compares behavior before and after changes to reveal SQL drift, extra HTTP calls, and performance regressions. Recorded executions become replayable JUnit 5 tests that run with standard Maven or Gradle tooling. The agent supports Java 8 through 21 and captures bytecode behavior without source changes. BitDive exposes runtime context and trace operations through MCP for Cursor, Windsurf, and Claude. It lists 49 supported technologies, including Spring Boot, PostgreSQL, MongoDB, Kafka, JUnit 5, Testcontainers, and Maven. Deployment options include hosted SaaS, on-premise, and air-gapped installations. Security details specify TLS 1.3 in transit, AES-256 at rest, and in-JVM masking of sensitive fields. Developer Use costs nothing; Company Rollout pricing is custom.