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@mcp-b/mcp-iframe wraps the iframe transport flow in a custom element. It is the package to use when you want to expose an iframe’s tools, prompts, or resources to the parent page without manually wiring transport classes.

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When to use this package

  • You want a parent page to surface capabilities from an iframe.
  • You prefer a declarative element over manual IframeParentTransport and IframeChildTransport setup.
  • You want namespaced tool forwarding tied to an element ID.

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When not to use this package

  • You need low-level control over message flow or custom transport wiring. Use @mcp-b/transports.
  • The iframe content does not expose navigator.modelContext or a compatible runtime.

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Where it sits in the package graph

This package sits on top of the iframe transport pair from @mcp-b/transports. It is a browser-facing convenience layer, not a separate transport protocol.

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First step

Expose navigator.modelContext inside the iframe, then import @mcp-b/mcp-iframe in the parent page and add the <mcp-iframe> element. The reference page documents events, attributes, methods, and namespacing behavior.

Reference

Element registration, attributes, methods, and event contract.

Bridge tools across iframes

Set up a parent-child iframe bridge step by step.

Transports overview

Inspect the underlying iframe transport classes.

Spec status and limitations

Background on cross-document exposure questions that still affect iframe behavior.