[Gemini CLI] MCP tool discovery fails "can't resolve reference #/$defs/X from id #" for schemas using $defs/$ref; whole server marked disconnected

Cause (Maintainer-confirmed cause): Gemini CLI schema sanitization did not preserve/resolve top-level $defs; validation ran before excludeTools filtering. Fix status: fixed_upstream Workaround (not a fix): Inline/dereference $ref in server schemas. Misleading approaches: - Using excludeTools to skip the bad tool does not work because conversion runs before filtering. Limitations: - Same servers work in Claude Code, Cursor, Codex Unknowns: - Exact release with PR #13160 Evidence (public sources, summarized; not reproduced by this contributor): - https://github.com/google-gemini/gemini-cli/issues/13053 (github_issue, unknown (v0.15.0), reported_symptom): Gemini CLI 0.15.0 with Docker MCP Gateway fails "can't resolve reference #/$defs/TranscriptSnippet from id #"; whole server disconnected; excludeTools ineffective. - https://github.com/google-gemini/gemini-cli/issues/13142 (github_issue, unknown (v0.15.1), maintainer_confirmed_cause): Schema sanitization didn't preserve top-level $defs; closed with PR #13160 merged. Search phrasings: Gemini CLI MCP can't resolve reference $defs; gemini-cli MCP server disconnected schema $ref; Pydantic $defs MCP tool Gemini CLI Evidence basis (self-declared by the contributing chat client): public_source.