Universal Tool Calling Protocol (UTCP) is unclaimed —

Universal Tool Calling Protocol (UTCP)

utcp.io

UTCP is a lightweight, secure, and scalable standard that lets AI agents and applications discover and call tools directly using their native protocols, without requiring wrapper servers. It extends OpenAPI with agent-focused metadata (tags, average_response_size, multi-protocol call templates) and lets tool providers publish a 'manual' describing how to call their existing APIs directly. It supports multiple communication protocols (HTTP, CLI, gRPC, GraphQL, SSE, text files, and MCP for interoperability) through a plugin-based architecture. Reference implementations are available as open-source libraries in Python, TypeScript, Go, and other languages.

What it's for

Discover and call tools directly using their native protocolsExpose existing REST APIs to AI agents without building wrapper serversAutomatically convert existing OpenAPI/Swagger specs into UTCP manualsEnable internal tool usage by AI systems within enterprisesConnect AI agents to internal and external servicesInteroperate with MCP (Model Context Protocol) servers

Features 13

@utcp_tool Python decorator to expose functions as UTCP tools with auto-generated schemas
Automatic conversion of OpenAPI/Swagger specs into UTCP manuals
Customizable Tool Search Strategy for discovering relevant tools
Direct tool calling without wrapper servers or middleman infrastructure
Manual discovery vs tool execution transport roles
Multi-protocol support: HTTP, CLI, gRPC, GraphQL, SSE, NDJSON, octet-stream, text files, and MCP
Namespacing of discovered tools by manual name
Pluggable Tool Repository for persistent storage of tool definitions
Plugin-based, extensible architecture for custom transport/protocol types
Reuses existing native authentication and security instead of reimplementing it
Tool tagging and average_response_size metadata for resource planning
UTCPManual JSON document describing available tools and how to call them
Variable substitution for secrets (env vars, .env files, secrets managers)

At a glance

open sourceself-hostableAPI

TypeLibrary / SDK

DeploymentSelf-hosted

Fortool providers, tool consumers, AI agent developers, application builders, enterprise developers, SaaS providers, enterprise teams, existing API owners

CompanyUTCP Contributors

Integrations

GitHubModel Context Protocol (MCP)

Resources

Docs