--- title: Turn your REST APIs into MCP tools with Google Cloud API... description: Google Cloud API Gateway now supports acting as a remote MCP server in Public Preview, letting teams expose existing REST APIs as agent-ready MCP tools by... canonical: https://daily.dev/posts/turn-your-rest-apis-into-mcp-tools-with-google-cloud-api-gateway-jg3qjmmtw twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Turn your REST APIs into MCP tools with Google Cloud API Gateway | daily.dev og:description: Google Cloud API Gateway now supports acting as a remote MCP server in Public Preview, letting teams expose existing REST APIs as agent-ready MCP tools by... og:url: https://daily.dev/posts/turn-your-rest-apis-into-mcp-tools-with-google-cloud-api-gateway-jg3qjmmtw og:image: https://api.daily.dev/og/posts/JG3qjmmTw.png og:image:alt: Turn your REST APIs into MCP tools with Google Cloud API Gateway og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Turn your REST APIs into MCP tools with Google Cloud API Gateway **[Google Developers](https://daily.dev/sources/googledevs)** · 4 min read · 0 upvotes · 0 comments ## Summary Google Cloud API Gateway now supports acting as a remote MCP server in Public Preview, letting teams expose existing REST APIs as agent-ready MCP tools by annotating their OpenAPI 3 specs with x-google-api-management.mcp and x-google-mcp-tool. No separate MCP server needs to be built or hosted: the gateway transcodes tools/call requests into REST calls, reusing existing JWT/API-key auth, quotas, and logging. The post walks through annotating operations, deploying, securing tools/list discovery with JWT (API keys cannot secure it), and connecting an ADK agent via StreamableHTTPConnectionParams. Current limits include no support for HTTP 204 responses, a 1,000-tool cap per gateway, and MCP being incompatible with model routing in the same config. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How do I expose an existing REST API as an MCP tool without building a separate MCP server? Google Cloud API Gateway can act as a remote MCP server in Public Preview by annotating the OpenAPI 3 spec you already deploy with x-google-api-management.mcp and x-google-mcp-tool. Deploying the config makes existing REST operations available as MCP tools on a /mcp base path, with tools/call transcoded into REST requests and existing JWT or API-key policies applied unchanged. _daily.dev surfaces practical guides like this for developers wiring REST backends into agent tooling._ ### How do I secure MCP tool discovery in Google Cloud API Gateway? By default tools/list is unauthenticated, exposing tool names and input schemas to anyone. For production, require a JWT via the security field under x-google-api-management.mcp.tools-list, since API keys cannot secure this method. tools/call always enforces whatever authentication the underlying REST operation already requires, regardless of discovery security. _Teams locking down agent-facing endpoints can track gateway security patterns like this on daily.dev._ ### What are the current limitations of MCP support in Google Cloud API Gateway? In Public Preview, operations returning empty bodies like HTTP 204 are not exposed as MCP tools, deeply nested object schemas may not render fully in tools/list, a single gateway supports up to 1,000 tools, and MCP cannot be enabled in the same API config as model routing. MCP resources, prompts, response streaming, and Model Armor payload inspection are planned but not yet available. _Developers evaluating agent-gateway tradeoffs can follow rollout limits like these on daily.dev._ ## Similar posts on daily.dev - [MCP Gateway for AI Agents: Connecting AI Agents to SaaS Tools Without Sharing Your Credentials using DigitalOcean Action Gateway](https://daily.dev/posts/mcp-gateway-for-ai-agents-connecting-ai-agents-to-saas-tools-without-sharing-your-credentials-using-efto06ch8) · DigitalOcean Community · 1 upvotes · 0 comments - [Azure API Management Adds Dedicated AI Gateway Tier, Governing Models and MCP Tools](https://daily.dev/posts/azure-api-management-adds-dedicated-ai-gateway-tier-governing-models-and-mcp-tools-cx4kwhecw) · InfoQ · 1 upvotes · 0 comments --- Tags: [#mcp](https://daily.dev/tags/mcp), [#rest-api](https://daily.dev/tags/rest-api), [#openapi](https://daily.dev/tags/openapi) [View this post on daily.dev](https://daily.dev/posts/turn-your-rest-apis-into-mcp-tools-with-google-cloud-api-gateway-jg3qjmmtw) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Turn your REST APIs into MCP tools with Google Cloud API Gateway","url":"https://daily.dev/posts/turn-your-rest-apis-into-mcp-tools-with-google-cloud-api-gateway-jg3qjmmtw","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/turn-your-rest-apis-into-mcp-tools-with-google-cloud-api-gateway-jg3qjmmtw"},"datePublished":"2026-09-24T16:17:48.020Z","dateModified":"2026-09-24T17:20:29.157Z","description":"Google Cloud API Gateway now supports acting as a remote MCP server in Public Preview, letting teams expose existing REST APIs as agent-ready MCP tools by...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/8fea4777935280556a888b693da90521?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/8fea4777935280556a888b693da90521?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Google Developers","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Google Developers","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1/logos/ea4bbded4e7f45ccb82e121a3156535f","url":"https://daily.dev/sources/googledevs"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/turn-your-rest-apis-into-mcp-tools-with-google-cloud-api-gateway-jg3qjmmtw","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"mcp,rest-api,openapi","timeRequired":"PT4M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Google Developers","item":"https://daily.dev/sources/googledevs"},{"@type":"ListItem","position":3,"name":"Turn your REST APIs into MCP tools with Google Cloud API Gateway"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/turn-your-rest-apis-into-mcp-tools-with-google-cloud-api-gateway-jg3qjmmtw#faq","mainEntity":[{"@type":"Question","name":"How do I expose an existing REST API as an MCP tool without building a separate MCP server?","acceptedAnswer":{"@type":"Answer","text":"Google Cloud API Gateway can act as a remote MCP server in Public Preview by annotating the OpenAPI 3 spec you already deploy with x-google-api-management.mcp and x-google-mcp-tool. 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