fix(mcp): prevent tool override name collisions

[Sehlani042]

Why are these changes needed?

McpWorkbench.tool_overrides validates renamed tools only against other configured overrides. It does not validate the final exposed names against the tools actually returned by the MCP server.

As a result, renaming fetch to an existing server tool name such as search can expose two schemas named search and route a real search call to fetch. A stale override for an original tool that is no longer present can cause the same wrong-route class by retaining a reverse mapping that shadows a present server tool.

This patch:

• validates exposed names against the actual list_tools result
• performs the validation before a direct call_tool can use renamed routing
• rebuilds reverse routing only from original tools currently present on the server
• adds regressions for real-name collisions, direct-call validation, and stale overrides

No public API or persistence format changes.

Related issue number

No existing issue covers this root cause. I also checked current open PRs before publication; #7594 changes schema handling and is unrelated.

Checks

• Documentation changes are not needed; this is an internal routing correctness fix.
• I've added tests corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

Verification

RED before the production change:

• the real-server-name collision regression failed because no ValueError was raised

GREEN after the change:

• related MCP workbench suites: 39 passed
• Ruff lint and format: passed
• Pyright: passed
• mypy: passed
• git diff --check: passed

The broader test_mcp_tools.py run reached 22 passed, 1 skipped with five external mcp-server-fetch / mcp-server-git failures. Those exact five failures reproduce on untouched main, so they are baseline environment noise rather than regressions from this patch.

AI assistance

This patch was prepared with Codex under the contributor's direction. Codex was used for issue/PR race checking, RED/GREEN implementation, current-main verification, and preparing this draft description.

[Sehlani042]

@microsoft-github-policy-service agree