fix(mcp): accept canonical resource names in path params and keep error results schema-valid

[harpchad]

Fixes #6107

Problem

The MCP tools substitute path parameters directly into the REST route, so memo_get_memo with memo: "memos/abc123" requests /api/v1/memos/memos/abc123 and 404s. But memos/abc123 is exactly what the API returns as name in every memo object — an MCP client that round-trips the name it received from memo_create_memo/memo_list_memos gets a 404 on every follow-up call, and for memo_update_memo the edit is silently lost.

The failure is then hidden by a second issue: on REST errors the tools return structuredContent: {"error": ...}, which doesn't conform to the tool's declared outputSchema (e.g. required state/content/visibility). Spec-strict clients (Claude Code, LiteLLM, the ChatGPT connector) reject the response with a schema-validation error, masking the underlying 404.

Changes

• substitutePathParameters now routes values through trimResourceNamePrefix: when a path parameter's placeholder directly follows its collection segment (/api/v1/memos/{memo}) and the value carries that collection prefix (memos/abc123), the prefix is stripped. Bare IDs pass through unchanged; foreign prefixes and multi-segment values are left untouched. Works generically for {memo}, {attachment}, and any future path parameter.
• newToolErrorResult no longer attaches structuredContent. Error results report through isError: true and text content, per the spec's structured-content guidance — structuredContent is only meaningful when it conforms to the declared output schema. As a bonus, clients now see the real error message (404 Not Found: memo not found) instead of a validation failure.

Testing

• New table-driven test TestBuildAPIRequestAcceptsResourceNamesForPathParameters covering canonical names, bare IDs, nested routes, attachment names, and the two left-untouched cases; updated error-shape assertions in adapter_test.go and service_test.go.
• go test ./server/router/mcp/... passes; go build ./... clean; golangci-lint run reports 0 issues.
• Verified end-to-end against a locally built server over the streamable HTTP endpoint: create → get/update/comment/list-comments/delete all succeed using full memos/<id> names (update verified persisted), and a nonexistent-memo call returns isError: true with no structuredContent and the real 404 message.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 385c2463-af37-4520-96b9-baf0c116af4a

📥 Commits

Reviewing files that changed from the base of the PR and between 41dd3d1 and 6db96ec.

📒 Files selected for processing (4)

• server/router/mcp/adapter.go
• server/router/mcp/adapter_test.go
• server/router/mcp/result.go
• server/router/mcp/service_test.go

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Walkthrough

MCP path substitution now accepts canonical resource names by removing collection prefixes before URL-escaping path identifiers. Tests cover bare IDs, canonical names, nested routes, and reserved characters. Tool errors now return text content with IsError: true while omitting StructuredContent; related adapter and service tests were updated accordingly.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title matches the main change: canonical resource-name handling and schema-valid tool errors.
Description check	✅ Passed	The description is clearly about the same MCP path-parameter and error-result fixes.
Linked Issues check	✅ Passed	The changes address #6107 by accepting canonical resource names and removing schema-invalid structuredContent from errors.
Out of Scope Changes check	✅ Passed	The added tests and helper logic are directly tied to the linked MCP fixes and do not appear unrelated.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[boojack]

LGTM