Callio is an API marketplace and gateway built specifically for AI agents. It serves as a unified interface that allows AI agents to discover, authenticate, and call any API through a single proxy, eliminating the need to manage individual API keys and custom integration code for each service.

The platform provides access to over 50 APIs across multiple categories including search, payments, email, data processing, messaging, analytics, cloud services, identity verification, social media, AI/ML models, developer tools, and storage. Key capabilities include automatic authentication injection, usage tracking, billing management, rate limiting, and routing. The system works with various AI development tools and frameworks through MCP (Model Context Protocol) compatibility.

Callio operates through a simple three-step process: users obtain a single API key that provides access to the entire marketplace, browse or let their agent search for appropriate APIs, and then execute calls through one unified endpoint. The platform handles all the underlying complexity including authentication, rate limits, and routing automatically.

The primary benefit is eliminating the infrastructure overhead of managing multiple API integrations, allowing developers to ship products faster. Use cases include giving AI agents real-world capabilities like web search, email sending, payment processing, and data enrichment without building custom integrations for each service.

The product targets three main user groups: AI developers building agent workflows who need to provide their agents with external API capabilities, API providers seeking distribution to AI agents without needing sales teams, and startups that want to ship quickly without infrastructure overhead. Integration is supported through REST proxy endpoints or MCP server installation for tools like Claude Code, Cursor, and Antigravity.