Turn your REST APIs into MCP tools with Google Cloud API Gateway

Google Cloud API Gateway now supports acting as a remote Model Context Protocol server in Public Preview, allowing teams to expose existing REST API operations as agent-callable tools without building and maintaining separate MCP infrastructure. By annotating OpenAPI 3.0 or 3.1 specifications, developers can let the gateway translate MCP JSON-RPC tool calls into REST requests while preserving existing authentication, quotas, logging, and policy enforcement. API Gateway serves MCP through a `/mcp` endpoint, supports tool discovery and invocation by MCP-compatible clients such as ADK and Gemini Enterprise, and can publish tools through API Hub and Agent Registry. Tool descriptions should explain when and why an agent should use an operation, while production deployments can protect tool discovery with JWT authentication and continue enforcing each REST operation’s existing security requirements. The feature is positioned as a lightweight option for services such as Cloud Run, alongside Apigee for broader enterprise API management and Agent Gateway for governing outbound agent calls. Current limitations include no support for OpenAPI 2.0, empty HTTP 204 responses, some deeply nested schemas, more than 1,000 tools per gateway, simultaneous use of MCP and model routing in one API configuration, and capabilities such as streaming, prompts, resources, and Model Armor inspection remaining on the roadmap.

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