API Development & Testing

CA

Castov

4.5/5.01 verified review

Free·Open Source·MIT

Fast, 100% client-side developer platform with CLI and MCP server support.

• 100% local browser and CLI execution with zero telemetry.
• Includes a native Model Context Protocol (MCP) server for Cursor and Claude.
• Over 60 interactive developer tools and chainable data pipelines.

1stars on GitHub

MA

MachineMail

4.4/5.01 verified review

Freemium·Open Source·MIT

Email API designed for AI agents and automated workflows.

• Free and dedicated mailboxes for autonomous agents.
• Built-in trust reports on incoming messages for security.
• Full compatibility with the MCP protocol and AgentMail API.

SP

Speechmatics

4.4/5.01 verified review

Freemium·Open Source·MIT

Voice AI APIs for enterprise-grade speech-to-text and transcription in 55+ languages.

• High accuracy with diverse accents.
• Flexible deployment options.
• Comprehensive enterprise compliance.

164stars on GitHub

IN

Insomnia

4.4/5.01 verified review

Freemium·Open Source·Apache-2.0

Collaborative API development and testing platform for HTTP, REST, GraphQL, and gRPC architectures.

• Native support for multiple protocols including REST, GraphQL, gRPC, and WebSockets
• Scratch Pad mode available without requiring user registration or login
• Tight Git version control integration for collection synchronization

40.1kstars on GitHub

RE

ReadMe

4.4/5.01 verified review

Paid·Open Source·MIT

Interactive technical documentation platform for APIs and developer tools.

• Automatic generation of API references from OpenAPI specs.
• Documentation components optimized for AI agent readability.
• Built-in version control and branch management features.

147stars on GitHub

TM

Tar Minefield

4.3/5.01 verified review

Free·Open Source·MIT

Test suite and documentation to standardize tar file extraction and prevent parsing discrepancies.

• Provides comprehensive test cases for tar parsers.
• Helps identify security vulnerabilities from parsing ambiguities.
• Promotes behavior convergence across programming languages.

6stars on GitHub

PO

Postman

4.3/5.01 verified review

Freemium·Open Source·Apache-2.0

Native API platform for development, testing, documentation, and agent automation.

• Broad protocol support including HTTP, GraphQL, gRPC, and WebSockets.
• Advanced tooling for automated testing and request collections.
• Native integration with coding agents through CLI and MCP servers.

24stars on GitHub

BA

Backlane

4.1/5.01 verified review

Free·Open Source·MIT

eCommerce MCP server connecting AI assistants directly to seller accounts.

• Native Model Context Protocol integration for popular AI assistants.
• Streamlined inventory and catalog queries directly inside development environments.
• Support for major European marketplace platforms like OTTO and Kaufland.

1stars on GitHub

FI

Fixrb

4.0/5.01 verified review

Freemium·Open Source·MIT

A Ruby testing framework where test suites are RFC 2119 specifications without class coupling.

• RFC 2119 specification approach for clearer test readability.
• Strict class decoupling using duck typing paradigms.
• Execution of each context within its own isolated process.

47stars on GitHub

VE

VelaTrace

4.0/5.01 verified review

Free·Open Source·MIT

A free KiCad board linter plugin designed to catch mistakes before ordering.

• Helps prevent costly mistakes before sending boards to fabrication
• Direct integration as a plugin within the KiCad environment
• Includes checks tailored for high-speed signal designs

4stars on GitHub

DE

DelightQL

4.0/5.01 verified review

Freemium·Open Source·Apache-2.0

An advanced query language that transpiles to SQL using functional and logic programming.

• Functional and logic programming syntax that simplifies complex queries.
• Direct transpilation to standard SQL compatible with multiple engines.
• WASM-based interactive execution built right into the documentation.

2stars on GitHub