fix(gateway): preserve structured tool results - #212
Closed
its-mash wants to merge 5 commits into
Closed
Conversation
![github-code-quality[bot]](https://avatars.githubusercontent.com/u/9919?s=60&v=4){kind=small}
Comment on lines
+38
to
+53
| import { | ||
| createSpace, | ||
| createFeatureSet, | ||
| installServer, | ||
| getDefaultSpace, | ||
| refreshRegistry, | ||
| enableServerV2, | ||
| emitEvent, | ||
| approveOAuthClient, | ||
| seedServerFeatures, | ||
| listFeatureSetsBySpace, | ||
| listServerFeatures, | ||
| listClients, | ||
| addFeatureToSet, | ||
| grantOAuthClientFeatureSet, | ||
| } from '../helpers/tauri-api'; |
Member
Author
|
Superseded — the contributor's original PR #206 has been reopened; this duplicate re-authored their work under my name. |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
Preserve
structuredContentand protocol-level_metawhen forwarding downstreamtools/callresults through the gateway.Problem
A downstream server can advertise an
outputSchemaand correctly return both textcontentandstructuredContent. The gateway previously reduced that response to onlycontentplusisErrorwhile routing it, then constructed a newCallToolResultfrom those two fields.Strict MCP clients consequently rejected otherwise successful tool calls with an error like:
This is not specific to one downstream implementation: it affects any tool that advertises an output schema and returns structured output.
Root cause
The result was narrowed at two gateway boundaries:
RoutingServiceconverted the downstreamCallToolResultinto a customToolCallResultcontaining onlycontentandis_error.Both transformations discarded
structured_content; protocol-levelmetawas discarded for the same reason.Fix
structured_contentandmetathroughToolCallResult.CallToolResultso both routing boundaries preserve the same fields.No downstream server changes are required.
Verification
cargo +1.88.0 fmt --all -- --checkcargo +1.88.0 test -p mcpmux-gateway— 145 passed, 0 failedcargo +1.88.0 build --release -p mcpmuxcontentandstructuredContentand pass client-side output validation.Scope
The patch is limited to the gateway result-conversion path and one regression test. It does not change downstream servers, tool schemas, permissions, or feature-set routing.