# API Client

One tool for intercepting, mocking, and replaying HTTP — acquired by BrowserStack

Requestly is a BrowserStack-backed API client, HTTP interceptor, mock server, and session replay tool for frontend and QA teams. Its current product is commercial/API-client led, while the legacy interceptor/open-source code is AGPLv3. The free plan covers individual workflows, and Pro lists at $12/user/month monthly or $9/user/month annually for collaborative QA and frontend debugging teams.

Beautiful documentation that converts

AI-powered documentation platform that transforms markdown into beautiful, searchable docs sites with minimal config. Features AI writing suggestions, auto API reference generation from OpenAPI specs, built-in analytics, versioning, custom domains, and a web editor for non-technical contributors. Supports MDX for interactive components. GitHub integration for CI/CD updates. Used by Anthropic, Cursor, Turso, and hundreds of developer-focused companies.

Self-hosted proxy API for routing AI CLI accounts into OpenAI-compatible endpoints

CLIProxyAPI is an open-source Go proxy server that wraps Gemini CLI, Claude Code, OpenAI Codex, Grok Build, and related CLI account flows behind OpenAI/Gemini/Claude-compatible API endpoints. Use it carefully: it can touch OAuth sessions, auth files, logs, and provider account policies, so production use needs credential and ToS review.

Open-source API client

Hoppscotch is a free, open-source API development ecosystem for building, testing, documenting, and collaborating on APIs through a lightweight, fast web-based interface. It supports REST, GraphQL, WebSocket, MQTT, SSE, and Socket.IO protocols across web, desktop, and CLI clients. With 79K+ GitHub stars, 2.5M+ users, and 5M+ monthly API requests, Hoppscotch has become a leading open-source alternative to Postman for developers who prioritize speed, simplicity, and self-hostable workflows.

MCP server for connecting AI assistants to Supabase projects

Supabase MCP is Supabase's Apache-2.0 server for connecting AI assistants to Supabase projects. It can expose database, configuration, and project-management workflows to MCP clients such as Cursor, Claude, and Windsurf, while the official docs emphasize permission and security review before production use, SQL changes, or high-privilege database access.

Build optimized documentation sites

Meta's open-source documentation framework built on React with MDX support, versioning, internationalization, and search. Powers documentation sites for many open-source projects with 58k+ GitHub stars. The standard choice for open-source projects that need professional documentation with minimal setup, offering blog support and plugin extensibility alongside core docs features.

MCP gateway and integration catalog for AI agents

Executor is an MIT-licensed integration layer and MCP gateway for AI agents. It gives Claude Code, Cursor, Codex, and other MCP-speaking clients one endpoint for connected OpenAPI specs, GraphQL APIs, MCP servers, Google Discovery sources, and custom JavaScript tools, with local, cloud, and self-hosted deployment options for teams centralizing tool access.

Open-source multi-protocol API client

Firecamp is an open-source API DevTool supporting REST, GraphQL, WebSocket, and Socket.IO protocols as a lightweight alternative to Postman. It provides IntelliSense, team collaboration with shared workspaces, and seamless import from OpenAPI, Insomnia, AsyncAPI, and HAR formats. Each protocol gets a dedicated testing playground with response metrics including time, size, and status codes.

Usage metering and billing infrastructure for AI, API, and SaaS products

Flexprice is an AGPL-3.0 open-source platform for real-time usage metering, usage-based pricing, credits, entitlements, and billing workflows. It helps engineering and finance teams turn token, API, and feature events into billable usage across managed-cloud or self-hosted deployments. Use it when a product needs finance-grade chargeback and customer usage controls, not only LLM traces.

HubSpot's hosted MCP server for CRM data and workflows.

HubSpot MCP Server is HubSpot's hosted remote MCP server for connecting compatible AI tools to CRM data. It uses OAuth 2.1 with PKCE through MCP auth apps, then exposes HubSpot context such as contacts, companies, deals, tickets, activities, and marketing or content objects according to user permissions, granted scopes, and sensitive-data restrictions in the account.

Intercom's remote MCP server for support and Help Center context.

Intercom MCP Server is Intercom's hosted remote MCP server for connecting AI tools to Intercom workspace data. It supports the recommended Streamable HTTP endpoint, OAuth or bearer-token authentication, and tools for conversations, contacts, companies, and Help Center article workflows, with access limited by token permissions and Intercom workspace policy.

MCP integration platform for agent tool use at scale

Klavis AI is an Apache-2.0 MCP integration platform for teams connecting AI agents to external SaaS tools and APIs. The public repo and official docs position it as infrastructure for reliable tool access at scale, so it fits teams that want reusable MCP connectors without treating every integration as a one-off script or custom OAuth maintenance project.

Real-time usage metering and billing for AI, API, and DevOps products

OpenMeter is an Apache-2.0 open-source metering platform that ingests usage events, aggregates them into meters, and supports limits, entitlements, and usage-based billing. It fits AI, API, and DevOps products that need token-level reporting, customer usage visibility, or finance-ready chargeback data. Teams can self-host the core platform or evaluate OpenMeter's managed offering.

World's largest API hub and marketplace

RapidAPI is the world's largest API hub and marketplace connecting developers to thousands of public and private APIs through a single platform. Provides a unified interface for discovering, testing, and managing API connections with standardized authentication, billing, and monitoring. Features an API testing playground, code snippets in multiple languages, team workspaces, and analytics dashboards. Used by millions of developers to integrate third-party services with a single API key.

Git-friendly API client by the creator of Insomnia

Yaak is an API client built by the original creator of Insomnia, designed with Git-friendly file storage from the ground up. API requests, environments, and collections are stored as human-readable files that version control naturally alongside application code. Supports REST, GraphQL, gRPC, and WebSocket with a clean, keyboard-driven interface focused on developer productivity.

Community MCP server for n8n node knowledge, workflow drafting, and validation

n8n-MCP is an independent, MIT-licensed community server that gives MCP-compatible assistants structured access to n8n node documentation, properties, templates, and workflow validation helpers. It is distinct from the existing n8n product page and covers the MCP layer used from clients such as Claude, Cursor, Windsurf, and Codex.

Official Python SDK for the xAI API

The xAI Python SDK is the official Python client for the xAI API, giving developers a direct way to build Grok-powered apps without relying on community proxies or unofficial wrappers. It supports synchronous and asynchronous Python clients for chat completions, streaming responses, function/tool calling, and multimodal workflows, making it a clean fit for backend services, agents, notebooks, and developer tools that need programmatic xAI access.