> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mcp-b.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# What is WebMCP? Browser tools for AI agents

> Learn how WebMCP lets websites expose structured tools to AI agents through browser APIs, authenticated sessions, and visible user interfaces.

WebMCP is a Community Group proposal that lets a web application publish
structured actions as tools for AI agents. The site defines the actions and
their inputs. The agent uses that contract instead of inferring behavior from
screenshots, DOM structure, or click sequences.

The browser is a useful home for these tools because the page already has the
application's state, authorization checks, and visible interface. A tool can
reuse that context without moving browser-only logic into a separate service.
The application still validates inputs, enforces permissions, and asks for
confirmation when the consequence warrants it.

```mermaid theme={null}
sequenceDiagram
  participant Site as Web application
  participant Context as Browser WebMCP context
  participant Agent as AI agent
  Site->>Context: Register structured tools
  Agent->>Context: Discover and invoke a tool
  Context->>Site: Run the registered handler
  Site-->>Context: Return a structured result
  Context-->>Agent: Return the result
```

## Learn about the proposal

The [Community Group draft](https://webmachinelearning.github.io/webmcp/) owns
the proposed JavaScript API. Chrome maintains the current [developer
overview](https://developer.chrome.com/docs/ai/webmcp), [user journey
guide](https://developer.chrome.com/docs/ai/webmcp/use-cases), and [WebMCP and
MCP comparison](https://developer.chrome.com/docs/ai/webmcp/compare-mcp).

The [WebMCP API sources](/reference/webmcp/standard-api) and
[declarative API sources](/reference/webmcp/declarative-api) route
implementation questions to their upstream owners. [WebMCP resources and
status](/explanation/design/spec-status-and-limitations) collects status,
security, inspection, and testing resources.

## Where MCP-B fits

MCP-B provides packages around the proposal, including a polyfill, React
bindings, transports, iframe bridges, and a local relay. Bridges can make page
tools available to MCP clients, but the browser document remains the execution
environment. MCP-B does not define the WebMCP proposal.

[WebMCP and MCP-B
extensions](/explanation/strict-core-vs-mcp-b-extensions) explains which
behavior belongs to this project. [Transports and
bridges](/explanation/architecture/transports-and-bridges) explains how those
packages cross browser boundaries.


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