ACI.dev is an open-source tool-calling platform from Aipotheosis Labs that connects AI agents to more than 600 tools and services through direct function calling or a unified MCP server. With roughly 4,900 stars on GitHub and active development into 2026, it handles the unglamorous but critical layer of agent building: authentication, permissions and reliable API access for tools like Google Calendar, Slack, GitHub and hundreds more.
Every agent project eventually needs to act in the real world, and every integration drags along OAuth flows, token storage and per-API quirks. ACI.dev centralizes that work: developers configure integrations once, and agents get intent-aware, permission-scoped access to the tools through a single interface. The project also powers VibeOps, which lets agentic IDEs provision and manage platforms such as Vercel, Supabase and Cloudflare through one MCP server. Its function-calling layer normalizes hundreds of third-party APIs into consistent, well-documented tool schemas, so model performance does not depend on each developer hand-writing wrappers and error handling for every service an agent needs to touch.
Free and open source under the Apache 2.0 license. The platform in this repository can be self-hosted at no cost, which is the listing this entry covers.
Agent developers and platform teams tired of rebuilding OAuth and API plumbing for every integration, who want their agents to use hundreds of real tools through one secure, permissioned layer.