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fix: ui/message accepts message array #119

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fix: ui/message accepts message array #119

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10 changes: 6 additions & 4 deletions specification/draft/apps.mdx
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Original file line number Diff line number Diff line change
Expand Up @@ -506,10 +506,12 @@ Host SHOULD open the URL in the user's default browser or a new tab.
method: "ui/message",
params: {
role: "user",
content: {
type: "text",
text: string
}
content: [
{
type: "text",
text: string
}
]
Comment on lines +509 to +514
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Copilot AI Dec 10, 2025

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The specification should document what content types are supported in the content array. While the PR description mentions supporting images (e.g., "prompting the agent with a text message and an image"), the spec only shows a single text content block.

Consider adding:

  1. A reference to the MCP SDK's ContentBlock type definition
  2. Documentation of supported content types (text, image, etc.)
  3. An example showing multiple content items in the array (e.g., text + image)

This would help implementers understand the full capabilities of this API and align with the stated goal of supporting additional use cases like multi-modal messages.

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@idosal idosal Dec 10, 2025

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@ochafik I see that the SDK supports ContentBlock as-is. There are types that are extremely cool and open up really interesting use cases, but I'm not sure hosts would know how to support and may require negotiation (e.g., audio, embedded resource). Should we limit it to text (and perhaps image if we add negotiation) for now?

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@ochafik ochafik Dec 11, 2025

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@idosal let's just make it all negotiable:

export interface McpUiHostCapabilities {
  /* @description Optional support for ui/message and its content types */
  messages?: {
    text?: {};
    image?: {};
    audio?: {};
    resource?: {};
    resourceLink?: {};
  }
  ...
}

cc/ @antonpk1 fyi

}
}

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