fix: MCP UI not rendering due to CallToolResult structure change #6143

aharvard · 2025-12-16T20:01:32Z

Summary

MCP UI was not rendering on main because the tool result structure changed from an array to an object.

Problem

The toolResult.value changed from:

Old format: Content[] (array directly)
New format: { content: Content[], structuredContent?, isError?, _meta? } (CallToolResult object)

The existing code expected toolResult.value to be an array, so getToolResultValue returned null and MCP UI resources were never rendered.

This regression was introduced by #6074 which changed the tool result structure to preserve full CallToolResult metadata.

Solution

Added typed interfaces for ToolResultData matching rmcp::model::CallToolResult (camelCase serialization)
Created getToolResultContent helper that:
- Extracts content array from the new structure
- Filters by audience annotation
Simplified toolResults assignment using the new helper

Testing

Tested with diagnostic session logs comparing 1.16 (working) vs main (broken) to verify the fix correctly extracts content from the new structure.

The tool result value changed from an array of Content to an object with a content property (CallToolResult from rmcp). This broke MCP UI rendering because the code expected toolResult.value to be an array directly. - Add typed interfaces for ToolResultData matching rmcp::model::CallToolResult - Create getToolResultContent helper that extracts content and filters by audience - Simplify toolResults assignment using the new helper

Copilot

Pull request overview

This PR fixes a critical bug where MCP UI resources were not rendering due to a structural change in tool results. The ToolResult<CallToolResult> structure changed from having value as a Content[] array directly to value being a CallToolResult object containing a content array field.

Updated TypeScript interfaces to match the new rmcp::model::CallToolResult structure with camelCase serialization
Created a new getToolResultContent helper function that correctly extracts content from the nested structure and applies audience filtering
Simplified tool results assignment in two locations to use the new helper

aharvard · 2025-12-16T20:19:38Z

This regression was introduced by #6074 which changed the tool result structure to preserve full CallToolResult metadata.

DOsinga

nice. think it can be simplified a bit

DOsinga · 2025-12-16T20:36:36Z

ui/desktop/src/components/ToolCallWithResponse.tsx

+  content: Content[];
+  structuredContent?: unknown;
+  isError?: boolean;
+  _meta?: unknown;


you should use the version we get from the api, not declare your own. I'm confused though since the API version doesn't seem to use camelCase?

DOsinga · 2025-12-16T20:45:41Z

ui/desktop/src/components/ToolCallWithResponse.tsx

+interface ToolResultError {
+  status: 'error';
+  error: string;
+}


I wouldn't bother with these since your doing a bunch of casting anyway

DOsinga · 2025-12-16T20:50:01Z

ui/desktop/src/components/ToolCallWithResponse.tsx

+
+type ToolResultData = ToolResultSuccess | ToolResultError;
+
+function getToolResultContent(toolResult: Record<string, unknown>): Content[] {


I think if you drop all the types, you can just go with

function getToolResultContent(toolResult: Record<string, unknown>): Content[] { if (toolResult.status !== 'success') { return []; } const value = toolResult.value as CallToolResponse; return value.content.filter((item) => { const annotations = (item as { annotations?: { audience?: string[] } }).annotations; return !annotations?.audience || annotations.audience.includes('user'); }); }

DOsinga · 2025-12-16T20:52:13Z

ui/desktop/src/components/ToolCallWithResponse.tsx

-    loadingStatus === 'success' && Array.isArray(toolResponse?.toolResult.value)
-      ? toolResponse!.toolResult.value.filter((item) => {
-          const audience = item.annotations?.audience as string[] | undefined;
-          return !audience || audience.includes('user');


good clean-up here

…interfaces Updated the getToolResultContent function to directly access the toolResult object, simplifying the logic. Removed unused TypeScript interfaces related to CallToolResultValue and ToolResultData, as they are no longer necessary with the new structure.

aharvard · 2025-12-16T21:01:35Z

feedback addressed, thanks!

DOsinga · 2025-12-16T21:11:58Z

ui/desktop/src/components/ToolCallWithResponse.tsx

+    const annotations = (item as { annotations?: { audience?: string[] } }).annotations;
+    return !annotations?.audience || annotations.audience.includes('user');
+  });
 }


this is fine, but casting the value to CallToolResponse from the api would be even better and avoid this sort of problem in the future

happy to address this, no prob!

Modified the ToolCallWithResponse component to import and utilize the CallToolResponse type for better type safety. Adjusted the getToolResultContent function to reflect this change, ensuring it correctly processes the tool result structure.

Copilot

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

* main: fix: we don't need to warn about tool count when in code mode (#6149) deps: upgrade agent-client-protocol to 0.9.0 (#6109) fix(providers): fix for gemini-cli on windows to work around cmd's multiline prompt limitations #5911 (#5966) More slash commands (#5858) fix: MCP UI not rendering due to CallToolResult structure change (#6143) fix: display shell output as static text instead of spinner (#6041) fix : Custom providers with empty API keys show as configured in desktop (#6105) Add .agents/skills and ~/.config/agent/skills to skills discovery paths (#6139) fix: use instructions for system prompt and prompt for user message in subagents (#6121) Fix compaction loop for small models or large input (#5803) feat: Centralize theme management with ThemeContext (#6137) OpenRouter & Xai streaming (#5873) fix: resolve mcp-hermit cleanup path expansion issue (#5953) feat: add goose PR reviewer workflow (#6124) perf: Avoid repeated MCP queries during streaming responses (#6138) Fix YAML serialization for recipes with special characters (#5796) Add more posthog analytics (privacy aware) (#6122) docs: add Sugar MCP server to extensions registry (#6077)

* origin/main: (57 commits) docs: create/edit recipe button (#6145) fix(google): Fix 400 Bad Request error with Gemini 3 thought signatures (#6035) fix: we don't need to warn about tool count when in code mode (#6149) deps: upgrade agent-client-protocol to 0.9.0 (#6109) fix(providers): fix for gemini-cli on windows to work around cmd's multiline prompt limitations #5911 (#5966) More slash commands (#5858) fix: MCP UI not rendering due to CallToolResult structure change (#6143) fix: display shell output as static text instead of spinner (#6041) fix : Custom providers with empty API keys show as configured in desktop (#6105) Add .agents/skills and ~/.config/agent/skills to skills discovery paths (#6139) fix: use instructions for system prompt and prompt for user message in subagents (#6121) Fix compaction loop for small models or large input (#5803) feat: Centralize theme management with ThemeContext (#6137) OpenRouter & Xai streaming (#5873) fix: resolve mcp-hermit cleanup path expansion issue (#5953) feat: add goose PR reviewer workflow (#6124) perf: Avoid repeated MCP queries during streaming responses (#6138) Fix YAML serialization for recipes with special characters (#5796) Add more posthog analytics (privacy aware) (#6122) docs: add Sugar MCP server to extensions registry (#6077) ...

…icing * 'main' of github.com:block/goose: (35 commits) docs: skills (#6062) fix: add conditional configuration for GOOSE_BIN_DIR in PATH (#5940) Update dependencies to help in Fedora packaging (#5835) fix: make goose reviewer less bad (#6154) docs: create/edit recipe button (#6145) fix(google): Fix 400 Bad Request error with Gemini 3 thought signatures (#6035) fix: we don't need to warn about tool count when in code mode (#6149) deps: upgrade agent-client-protocol to 0.9.0 (#6109) fix(providers): fix for gemini-cli on windows to work around cmd's multiline prompt limitations #5911 (#5966) More slash commands (#5858) fix: MCP UI not rendering due to CallToolResult structure change (#6143) fix: display shell output as static text instead of spinner (#6041) fix : Custom providers with empty API keys show as configured in desktop (#6105) Add .agents/skills and ~/.config/agent/skills to skills discovery paths (#6139) fix: use instructions for system prompt and prompt for user message in subagents (#6121) Fix compaction loop for small models or large input (#5803) feat: Centralize theme management with ThemeContext (#6137) OpenRouter & Xai streaming (#5873) fix: resolve mcp-hermit cleanup path expansion issue (#5953) feat: add goose PR reviewer workflow (#6124) ...

Copilot AI review requested due to automatic review settings December 16, 2025 20:01

Copilot started reviewing on behalf of aharvard December 16, 2025 20:02 View session

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DOsinga approved these changes Dec 16, 2025

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Copilot AI review requested due to automatic review settings December 16, 2025 21:47

Copilot started reviewing on behalf of aharvard December 16, 2025 21:48 View session

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aharvard merged commit 07de82b into main Dec 16, 2025
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aharvard deleted the fix/mcp-ui-tool-result-structure branch December 16, 2025 21:54

github-actions bot mentioned this pull request Dec 19, 2025

chore(release): release version 1.18.0 (minor) #6194

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fix: MCP UI not rendering due to CallToolResult structure change #6143

fix: MCP UI not rendering due to CallToolResult structure change #6143

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aharvard commented Dec 16, 2025 •

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		type ToolResultData = ToolResultSuccess \| ToolResultError;

		function getToolResultContent(toolResult: Record<string, unknown>): Content[] {

fix: MCP UI not rendering due to CallToolResult structure change #6143

fix: MCP UI not rendering due to CallToolResult structure change #6143

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aharvard commented Dec 16, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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aharvard commented Dec 16, 2025

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aharvard commented Dec 16, 2025 •

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