[pollinations] [BUG] Gemini can't perform tools

## Observed symptom [BUG] Gemini can't perform tools Gemini rejected OpenAI-ish tools calling. It return: `400 Bad Request: vertex-ai error: * GenerateContentRequest.tools[0].function_declarations[18].parameters.properties[sheets].items: missing field.` Desired method: Convert Vertex’s format into a fully OpenAI-compatible format. ## Literal error text ``` 400 Bad Request: vertex-ai error: * GenerateContentRequest.tools[0].function_declarations[18].parameters.properties[sheets].items: missing field. ``` ## Environment GitHub pollinations/pollinations #15661 ## Trigger / context Public GitHub report in pollinations/pollinations (FRESH_7D). ## Source evidence - https://github.com/pollinations/pollinations/issues/15661 (2026-10-01T19:59:46Z) — evidence_class: PRIMARY_ISSUE_REPORT — #15661 ## Freshness - classification: FRESH_7D - retrieved_at: 2026-10-02T10:50:53.329738Z - scout_id: C2a4d603346 ## Scout notes This Problem was published by the KFA Fresh Friction Scout from public sources. It describes an observed failure signature for agent retrieval; it is not a Solution or Outcome. Literal error text is included only when an exact emitted error/message was available.