Open Source JavaScript MCP Clients

Klavis AI is a Y Combinator X25-backed open-source infrastructure platform that enables AI agents to reliably connect with external tools and services at scale through Model Context Protocol (MCP). Founded by ex-Google DeepMind and ex-Lyft engineers, Klavis provides 50+ production-ready MCP servers with enterprise OAuth support for GitHub, Slack, Gmail, Salesforce, Linear, Notion, and more. The flagship product Strata solves tool overload through progressive discovery, achieving +13% higher accuracy and 83%+ success on complex workflows. Developers can integrate via Python/TypeScript SDKs or REST API, with support for OpenAI, Claude, Gemini, LangChain, LlamaIndex, and CrewAI. Features include built-in authentication, multi-tenancy, hosted servers, Docker support, and enterprise security guardrails. Licensed under Apache 2.0, Klavis simplifies AI development by eliminating complex authentication management and enabling seamless workflow automation across multiple applications.

CodinIT.dev is a free, local, open source AI app builder that lets you go from idea to full-stack application entirely on your machine, no coding required, just chat with AI. You can build unlimited apps with real-time previews, instant undo, and responsive, frictionless workflows. Deep Supabase integration means you can create UI and backend logic in one cohesive environment, while the model-agnostic architecture lets you connect to any AI, whether cloud-based (Gemini 3 Pro, GPT-5, Claude Sonnet 4.5) or local via Ollama, so you’re never locked in. All source code remains on your device and integrates seamlessly with your preferred IDE. A natural-language API enables powerful data queries and updates, automating tasks without leaving the chat interface. By running entirely locally, CodinIT.dev delivers maximum privacy, minimal latency, and smooth developer experiences free from cloud-based inconsistencies.

Frontman is an open-source AI coding agent that lives inside your running web app. Click any element, describe the change, and Frontman edits the real source files with hot reload. Unlike IDE-only coding tools, Frontman sees the live DOM, component tree, computed CSS, routes, source maps, screenshots, console output, and server logs. That runtime context helps product managers, designers, and frontend teams fix copy, spacing, colors, layout bugs, and internal UI polish without guessing which file owns a rendered element. Works with Next.js, Astro, Vite, React, Vue, Svelte, and SvelteKit. BYOK model support includes OpenAI, Anthropic, OpenRouter, Google, xAI, Fireworks, NVIDIA, and more. Use Frontman when visual frontend edits get stuck in design QA, product review, or developer handoff.