Choose a runtime

Start with the live WebMCP proposal and current browser support. Add MCP-B packages only for the compatibility, type inference, or extension behavior your application needs.

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Choose in order

1. Does the target browser provide the WebMCP behavior you need? Check WebMCP resources and status. If yes, you may not need a runtime package.
2. Do you only need ambient types for the live proposal? Use the Community Group’s webmcp-types package.
3. Do you need MCP-B compatibility types or schema inference? Use @mcp-b/webmcp-types.
4. Do you need browser tool registration and discovery where native support is unavailable? Use @mcp-b/webmcp-polyfill.
5. Do you need MCP bridge transport, listTools, prompts, resources, or direct MCP server access? Use @mcp-b/global.
6. Do you only need React tool registration? Use usewebmcp.
7. Do you need React prompt, resource, or MCP client/provider hooks? Use @mcp-b/react-webmcp. Prompt and resource hooks require @mcp-b/global; tool hooks work with native or polyfilled document.modelContext, and client/provider hooks use their configured MCP connection.

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Package comparison

The two MCP-B runtime packages expose a descriptor-based executeTool() method that accepts serialized JSON. The live proposal currently uses object input. Feature-detect the method and follow the selected runtime’s reference for its implemented signature.

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Continue with the selected path

• For native behavior and ambient proposal types, use the WebMCP API sources.
• For the standalone polyfill, follow the @mcp-b/webmcp-polyfill overview and first tool tutorial.
• For the full MCP-B runtime, follow the @mcp-b/global overview and reference.
• For React, compare usewebmcp with @mcp-b/react-webmcp, then use the React tutorial.
• For schema inference and MCP-B type contracts, use the @mcp-b/webmcp-types reference.

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How the layers relate

For the layering rationale, see Runtime Layering. WebMCP and MCP-B extensions describes the package boundary.