WebMCP

WebMCP is an open source JavaScript library designed to enable websites to integrate with the Model Context Protocol (MCP). It introduces a widget—displayed as a small blue square in the bottom right corner of a web page—that allows users to connect to and interact with the website through a large language model (LLM) or agent. This setup facilitates interactions between users and the website using MCP clients, which can be configured to connect to WebMCP-enabled sites.

For website developers, WebMCP is added by including its script on the page. Once included, the widget initializes automatically, providing immediate access to its features. The library supports registering custom tools that LLMs can use to perform actions on the website. Tools are defined with specific parameters and descriptions, and can be registered programmatically. Prompts can also be registered, serving as predefined templates for common LLM queries, with support for dynamic arguments. Additionally, WebMCP allows developers to register resources, exposing data or content from the website—such as the current page’s HTML or specific DOM element content—through URIs for use in LLM interactions.

WebMCP handles sampling requests, enabling servers to request LLM completions via the client. When such a request is received, the widget displays a modal dialog prompting the user for input, which is then sent back to the server. This approach is designed to maintain security and privacy by involving human oversight in the completion process.

The tool is open source, as stated in its documentation, and is aimed at website developers who want to add MCP-based LLM or agent interactions to their sites. Its integration process is straightforward, relying on the inclusion of a JavaScript file and initialization via the provided widget, with further customization and tool registration possible through the WebMCP API.