WebMCP WebMCP Draft Community Group Report , 12 February 2026 More details about this document This version: https://webmachinelearning.github.io/webmcp Issue Tracking: GitHub Editors: Brandon Walderman ( Microsoft ) Khushal Sagar ( Google ) Dominic Farolino ( Google ) Copyright © 2026 the Contributors to the WebMCP Specification, published by the Web Machine Learning Community Group under the W3C Community Contributor License Agreement (CLA) . A human-readable summary is available. Abstract The WebMCP API enables web applications to provide JavaScript-based tools to AI agents. Status of this document This specification was published by the Web Machine Learning Community Group . It is not a W3C Standard nor is it on the W3C Standards Track. Please note that under the W3C Community Contributor License Agreement (CLA) there is a limited opt-out and other conditions apply. Learn more about W3C Community and Business Groups . 1. Introduction WebMCP API is a new JavaScript interface that allows web developers to expose their web application functionality as “tools” – JavaScript functions with natural language descriptions and structured schemas that can be invoked by agents , browser’s agents , and assistive technologies . Web pages that use WebMCP can be thought of as Model Context Protocol [MCP] servers that implement tools in client-side script instead of on the backend. WebMCP enables collaborative workflows where users and agents work together within the same web interface, leveraging existing application logic while maintaining shared context and user control. 2. Terminology An agent is an autonomous assistant that can understand a user’s goals and take actions on the user’s behalf to achieve them. Today, these are typically implemented by large language model (LLM) based AI platforms , interacting with users via text-based chat interfaces. A browser’s agent is an agent provided by or through the browser that could be built directly into the browser or hosted by it, for example, via an extension or plug-in. An AI platform is a provider of agentic assistants such as OpenAI’s ChatGPT, Anthropic’s Claude, or Google’s Gemini. 3. Security and privacy considerations 4. Accessibility considerations 5. API 5.1. Extensions to the Navigator Interface The Navigator interface is extended to provide access to the ModelContext . partial interface Navigator { [ SecureContext , SameObject ] readonly attribute ModelContext modelContext ; }; 5.2. ModelContext Interface The ModelContext interface provides methods for web applications to register and manage tools that can be invoked by agents . [ Exposed = Window , SecureContext ] interface ModelContext { undefined provideContext ( optional ModelContextOptions options = {}); undefined clearContext (); undefined registerTool ( ModelContextTool tool ); undefined unregisterTool ( DOMString name ); }; navigator . modelContext . provideContext(options) Registers the provided context (tools) with the browser. This method

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