Callio

For AI agent developers who need many APIs with different keys, Callio provides one key and proxy to call APIs so they can add real-world actions to agents fast

Callio is an API gateway built for AI agent workflows. It provides a unified proxy to connect agents to external APIs quickly while handling practical integration concerns such as authentication, key management, and rate limits, reducing the overhead of building and maintaining multi-API access.

• single API key for many APIs
• unified proxy endpoint by API slug
• API discovery and browsing
• stores provider keys securely
• MCP server for Claude Code and Cursor
• built-in rate limits and usage tracking