fix(gateway): OpenAPI tool failures return 400/404 instead of 200 (SBS-937) by btsouth · Pull Request #857 · btsouth/toolport

btsouth · 2026-09-03T23:24:34Z

What and why

The gateway's OpenAPI surface (POST /{tool}, used by Open WebUI, n8n and generated OpenAPI clients) never inspected the MCP result's isError flag. A timeout, a HITL deny, a downstream failure or an unknown tool name all returned HTTP 200 with the error text as a JSON string, so clients that branch on status ran their success path. The spec already documented 400 for a failed call and 404 for an unknown tool.

openapi_status reads result.isError; a true flag becomes 400, or 404 when the text carries the router's no route for tool '<name>' wording for the requested name.
Error responses use the same {"error": ...} body shape the spec's err_resp describes.
MCP stdio and /mcp are untouched; they already carry isError correctly.
Spec text for 400 now lists the failure kinds it covers.

Testing

cargo test --no-default-features --bin toolport-gateway openapi (unit test on the status mapping plus an end-to-end POST asserting 200 / 404 through handle_http)
cargo fmt --check
Full CI on this PR

Note

Medium Risk
Changes HTTP semantics for OpenAPI consumers (intentional spec alignment) and tightens scoped-client responses so out-of-scope tool names return 404 without executing; MCP paths are untouched.

Overview
OpenAPI POST /{tool} now maps MCP outcomes to real HTTP status codes instead of always returning 200 with error text as a JSON string. After a successful JSON-RPC envelope, the gateway reads result.isError and returns 400 for a failed call on a known tool, 404 for errors on an unknown name, and keeps 200 only for success; non-200 bodies use {"error": ...} so Open WebUI, n8n, and generated clients can branch on status as the spec describes. MCP stdio and /mcp are unchanged.

Tool “known” is decided separately from error wording via openapi_tool_is_known: meta-tools, in-scope live routes, grouped help targets, and (for unscoped callers) catalog entries count as known, so a real tool’s error message cannot be mistaken for “no route.” Scoped HTTP clients treat out-of-scope tools like missing ones (404, no dispatch), preserving the inventory boundary.

The generated OpenAPI doc’s 400 description now mentions timeouts and denials; CHANGELOG documents the fix (SBS-937). Unit and handle_http integration tests cover status mapping and scoped 404 behavior.

^{Reviewed by Cursor Bugbot for commit a90790d. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Return 400/404 for failed OpenAPI tool calls in `toolport-gateway` instead of 200

openapi_status now maps the MCP result isError flag to HTTP status: 200 for success, 400 for failed known tools, and 404 for unknown or out-of-scope tools.
openapi_tool_is_known classifies a tool name as known based on fixed meta-tools, in-scope live routes, and applicable catalog entries; scoped callers do not match out-of-scope catalog entries.
handle_http_with_headers returns a generic unknown-tool error body for 404s and wraps result text in an error envelope for 400s; successful results still return 200 with JSON text.
The generated OpenAPI spec now documents HTTP 400 for tool errors, timeouts, and denied calls.
Risk: openapi_tool_is_known scope logic means a scoped client that previously received a 200 with an error payload for an out-of-scope tool now gets a 404 with a generic body — clients parsing the old error text on hidden tools will break.

^{Macroscope summarized 5f35045.}

cursor · 2026-09-03T23:24:43Z

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coderabbitai · 2026-09-03T23:29:58Z

📝 Walkthrough

Walkthrough

The gateway now maps MCP tool-call results to HTTP 200, 400, or 404 responses. Error responses include result text. Tests cover successful, failed, timed-out, denied, and unknown tool calls.

Changes

OpenAPI status mapping

Layer / File(s)	Summary
Result status classification `src-tauri/src/bin/toolport-gateway.rs`	The gateway documents tool errors, timeouts, and denied calls as 400 responses. `openapi_status` maps successful, failed, and unknown-tool results to HTTP statuses.
HTTP response handling and validation `src-tauri/src/bin/toolport-gateway.rs`	The POST handler returns serialized success bodies or JSON errors with status 400 or 404. Tests cover status classification, response bodies, tool-name collisions, and dispatch counts.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: 🔵 Low · up to 1a508

Nested calls through toolport_call_tool can report an unknown inner tool as HTTP 400 instead of the documented HTTP 404, causing clients to receive the wrong failure classification. This should be corrected before merge.

Suggested reviewers: bharadwajkanneveti, forever-ivy

Sequence Diagram(s)

sequenceDiagram
  participant OpenAPI_POST_handler
  participant tool_router
  participant MCP_tool
  OpenAPI_POST_handler->>tool_router: Dispatch tool call
  tool_router->>MCP_tool: Execute selected tool
  MCP_tool-->>tool_router: Return MCP result
  tool_router-->>OpenAPI_POST_handler: Return result or unknown-tool error
  OpenAPI_POST_handler->>OpenAPI_POST_handler: Map result to HTTP status and response body

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: OpenAPI tool failures now return HTTP 400 or 404 instead of 200.
Description check	✅ Passed	The description directly explains the status mapping, error response format, affected endpoint, unchanged paths, specification updates, and tests.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (1 skipped: 1 too large.)

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Actionable comments posted: 1

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Inline comments:
In `@src-tauri/src/bin/toolport-gateway.rs`:
- Around line 13945-13953: Update the nested tool dispatch status-classification
flow around unwrap_call_tool, execute_call, and openapi_status so it passes the
effective dispatched tool name rather than the URL path segment. Ensure unknown
inner tools whose result is “no route for tool '<inner>'” are classified as HTTP
404, while preserving existing status handling for direct tool requests.

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src-tauri/src/bin/toolport-gateway.rs

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cursor · 2026-09-03T23:39:16Z

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cursor · 2026-09-03T23:41:19Z

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… result text Review of #857: matching the router's "no route" wording in the result text turned a real tool's error that happened to echo it into a 404. The handler now asks whether the requested name resolves at all (a meta-tool, a grouped browse tool, a live route, or a catalog entry) and uses only that and the isError flag to pick 400 or 404.

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Stale comment

Agentic security review of the OpenAPI 400/404 mapping on POST /{tool}. One medium finding: scoped HTTP clients can distinguish out-of-scope catalogued tools from unknown names via status code.

_{Sent by Cursor Security Agent: Security Reviewer (1)}

cursor · 2026-09-04T00:02:40Z

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…to 404 (SBS-937) The OpenAPI POST handler translated every tools/call envelope into HTTP 200 and only checked the JSON-RPC error slot, which MCP reserves for protocol errors. A timeout, a denied destructive call, a downstream failure or a misspelt tool name all arrived as 200 with the error text as a JSON string, so Open WebUI, n8n and generated clients ran their success path. The spec already promised 400 and 404 for those cases; the handler now honours it by reading the result's isError flag, with the router's no-route wording as the unknown-tool signal.

… result text Review of #857: matching the router's "no route" wording in the result text turned a real tool's error that happened to echo it into a 404. The handler now asks whether the requested name resolves at all (a meta-tool, a grouped browse tool, a live route, or a catalog entry) and uses only that and the isError flag to pick 400 or 404.

…ames

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…rver never leaks

devin-ai-integration Bot reviewed Sep 3, 2026

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Comment thread src-tauri/src/bin/toolport-gateway.rs Outdated

coderabbitai Bot reviewed Sep 3, 2026

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Comment thread src-tauri/src/bin/toolport-gateway.rs

btsouth force-pushed the fix/openapi-error-status branch from 1a508d2 to 7908928 Compare September 3, 2026 23:39

btsouth force-pushed the fix/openapi-error-status branch from 7908928 to b094061 Compare September 3, 2026 23:41

cursor Bot reviewed Sep 3, 2026

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Comment thread src-tauri/src/bin/toolport-gateway.rs Outdated

btsouth added 3 commits September 3, 2026 22:06

fix(gateway): keep the OpenAPI 404 from revealing out-of-scope tool n…

a90790d

…ames

btsouth force-pushed the fix/openapi-error-status branch from 6aaf776 to a90790d Compare September 4, 2026 02:06

cursor Bot reviewed Sep 4, 2026

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Comment thread src-tauri/src/bin/toolport-gateway.rs

fix(gateway): give the OpenAPI 404 a fixed body so a hidden tool's se…

5f35045

…rver never leaks

btsouth merged commit bd77be0 into main Sep 4, 2026
18 of 19 checks passed

btsouth deleted the fix/openapi-error-status branch September 4, 2026 02:40

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What and why

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Return 400/404 for failed OpenAPI tool calls in toolport-gateway instead of 200

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Walkthrough

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btsouth commented Sep 3, 2026 •

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Return 400/404 for failed OpenAPI tool calls in `toolport-gateway` instead of 200

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