> ## 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.

# WebMCP API sources

> Quick lookup for the sources that own the document-first WebMCP surface.

`document.modelContext` belongs to the evolving WebMCP Community Group
proposal. Use the source that owns the behavior you need.

## Platform and implementation sources

| Need | Source |
| - | - |
| Proposed interface, dictionaries, and algorithms | [WebMCP Community Group draft](https://webmachinelearning.github.io/webmcp/) |
| Chrome's implemented imperative behavior | [Chrome imperative API](https://developer.chrome.com/docs/ai/webmcp/imperative-api) |
| Codex site tools behavior | [OpenAI site tools documentation](https://learn.chatgpt.com/docs/webmcp) |
| Independent Codex compatibility snapshot | [Codex site tools compatibility](/reference/webmcp/codex-site-tools) |
| Browser and agent availability | [WebMCP implementation status](https://github.com/webmachinelearning/webmcp/blob/main/implementation-status.md) |
| Executable browser conformance | [Web Platform Tests](https://wpt.fyi/results/webmcp) |
| Ambient TypeScript declarations | [Upstream `webmcp-types`](https://github.com/webmachinelearning/webmcp-types) |
| Open design and specification work | [WebMCP issue tracker](https://github.com/webmachinelearning/webmcp/issues) |

<Warning>
  The proposal and browser implementations can differ while changes land. Use the Community Group
  draft for the proposed API, and use implementation docs and tests for browser compatibility.
</Warning>

## MCP-B package behavior

MCP-B package references describe the code shipped by this project. They do
not redefine the proposal.

| Package surface | Reference |
| - | - |
| MCP-B adapter extensions and schema helpers | [`@mcp-b/webmcp-ts-sdk`](/packages/webmcp-ts-sdk/reference) |
| Portable runtime behavior | [`@mcp-b/webmcp-polyfill`](/packages/webmcp-polyfill/reference) |

MCP-B packages can lag the live draft or extend it.

Use [WebMCP and MCP-B extensions](/explanation/strict-core-vs-mcp-b-extensions)
for the boundary and [Choose a runtime](/how-to/choose-runtime) for package
selection.


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