fix(apps): forward _meta in tool results to MCP Apps#7476
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The McpAppToolResult type and appToolResult memo were missing the _meta property, causing it to be silently dropped when converting tool results for the @mcp-ui/client SDK's AppRenderer component. This is a regression from #7013 which refactored McpAppRenderer to use the SDK's AppRenderer. The custom McpAppToolResult type was created without _meta, and the conversion logic only mapped content and structuredContent. Fixes #7435
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Pull request overview
This PR fixes a regression from #7013 where the _meta property from tool results was being dropped when forwarding to MCP Apps. The MCP Apps specification requires hosts to forward the entire tool execution result, including _meta, to the app view. The fix adds the missing _meta field to the McpAppToolResult type and ensures it's properly forwarded in the conversion logic.
Changes:
- Add
_meta?: { [key: string]: unknown }toMcpAppToolResulttype definition - Forward
_metaproperty in theappToolResultmemo when converting toCallToolResult
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| ui/desktop/src/components/McpApps/types.ts | Add optional _meta field to McpAppToolResult type |
| ui/desktop/src/components/McpApps/McpAppRenderer.tsx | Forward _meta from toolResult to appToolResult in the conversion memo |
| @@ -40,6 +40,7 @@ export type McpAppToolCancelled = McpUiToolCancelledNotification['params']; | |||
| export type McpAppToolResult = { | |||
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do we need this type? isn't this just CallToolResult?
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No, we don't, but upon further investigation, we are sending camel case over the wire and should make updates in the backend. Will follow up with another PR for that.
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Signed-off-by: Oleg Levchenko <[email protected]>
Summary
Fixes #7435
The
_metaproperty from tool results was being silently dropped when forwarding to MCP Apps via the@mcp-ui/clientSDK'sAppRenderercomponent. This is a regression introduced in #7013.Root Cause
When #7013 refactored
McpAppRendererto use the SDK'sAppRenderer, the customMcpAppToolResulttype was created without_meta, and the conversion logic in theappToolResultmemo only mappedcontentandstructuredContent.The upstream data (from rmcp's
CallToolResult) does include_metaon the wire — it was just being discarded at the TypeScript boundary.Changes
types.ts: Add_meta?: { [key: string]: unknown }toMcpAppToolResultMcpAppRenderer.tsx: Forward_metain theappToolResultmemoTesting
toolResult._meta