fix(tools): Handle JSON Schema boolean schemas in Gemini schema conversion by onematchfox · Pull Request #4531 · google/adk-python

onematchfox · 2026-02-18T14:23:54Z

Problem:
JSON Schema allows true and false as valid boolean schemas, where true accepts any value and false rejects all values. Some MCP servers use this pattern for unconstrained fields. E.g. mcp-grafana - see grafana-mcp-list-tools.json which was obtained from tools/list

The schema sanitizer previously passed booleans through unchanged, causing a Pydantic ValidationError when _ExtendedJSONSchema tried to validate them as schema objects.

1 validation error for _ExtendedJSONSchema
properties.data.items.properties.model
  Input should be a valid dictionary or object to extract fields from [type=model_attributes_type, input_value=True, input_type=bool]
    For further information visit https://errors.pydantic.dev/2.12/v/model_attributes_type
Traceback (most recent call last):
  ...
  File "/.foo/.venv/lib/python3.13/site-packages/google/adk/runners.py", line 561, in run_async
    async for event in agen:
      yield event
  File "/.foo/.venv/lib/python3.13/site-packages/google/adk/runners.py", line 549, in _run_with_trace
    async for event in agen:
      yield event
  File "/.foo/.venv/lib/python3.13/site-packages/google/adk/runners.py", line 778, in _exec_with_plugin
    async for event in agen:
    ...<64 lines>...
        yield event
  File "/.foo/.venv/lib/python3.13/site-packages/google/adk/runners.py", line 538, in execute
    async for event in agen:
      yield event
  File "/.foo/.venv/lib/python3.13/site-packages/google/adk/agents/base_agent.py", line 294, in run_async
    async for event in agen:
      yield event
  File "/.foo/.venv/lib/python3.13/site-packages/google/adk/agents/llm_agent.py", line 468, in _run_async_impl
    async for event in agen:
    ...<5 lines>...
        should_pause = True
  File "/.foo/.venv/lib/python3.13/site-packages/google/adk/flows/llm_flows/base_llm_flow.py", line 427, in run_async
    async for event in agen:
      last_event = event
      yield event
  File "/.foo/.venv/lib/python3.13/site-packages/google/adk/flows/llm_flows/base_llm_flow.py", line 446, in _run_one_step_async
    async for event in agen:
      yield event
  File "/.foo/.venv/lib/python3.13/site-packages/google/adk/flows/llm_flows/base_llm_flow.py", line 578, in _preprocess_async
    await tool.process_llm_request(
        tool_context=tool_context, llm_request=llm_request
    )
  File "/.foo/.venv/lib/python3.13/site-packages/google/adk/tools/base_tool.py", line 129, in process_llm_request
    llm_request.append_tools([self])
    ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
  File "/.foo/.venv/lib/python3.13/site-packages/google/adk/models/llm_request.py", line 255, in append_tools
    declaration = tool._get_declaration()
  File "/.foo/.venv/lib/python3.13/site-packages/google/adk/tools/mcp_tool/mcp_tool.py", line 200, in _get_declaration
    parameters = _to_gemini_schema(input_schema)
  File "/.foo/.venv/lib/python3.13/site-packages/google/adk/tools/_gemini_schema_util.py", line 218, in _to_gemini_schema
    json_schema=_ExtendedJSONSchema.model_validate(sanitized_schema),
                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^
  File "/.foo/.venv/lib/python3.13/site-packages/pydantic/main.py", line 716, in model_validate
    return cls.__pydantic_validator__.validate_python(
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
        obj,
        ^^^^
    ...<5 lines>...
        by_name=by_name,
        ^^^^^^^^^^^^^^^^
    )
    ^
pydantic_core._pydantic_core.ValidationError: 1 validation error for _ExtendedJSONSchema
properties.data.items.properties.model
  Input should be a valid dictionary or object to extract fields from [type=model_attributes_type, input_value=True, input_type=bool]
    For further information visit https://errors.pydantic.dev/2.12/v/model_attributes_type

Solution:

Convert boolean schemas to {"type": "object"} as the closest approximation available in Gemini's schema model.

Testing Plan

Unit Tests:

I have added or updated unit tests for my change.
All unit tests pass locally.

============================= test session starts ==============================
platform linux -- Python 3.13.5, pytest-9.0.2, pluggy-1.6.0
plugins: asyncio-1.3.0, xdist-3.8.0, mock-3.15.1, anyio-4.12.1
asyncio: mode=Mode.AUTO

tests/unittests/tools/test_gemini_schema_util.py: 65 passed in 1.48s
=============================== 65 passed in 1.48s ==============================

Checklist

I have read the CONTRIBUTING.md document.
I have performed a self-review of my own code.
I have commented my code, particularly in hard-to-understand areas.
I have added tests that prove my fix is effective or that my feature works.
New and existing unit tests pass locally with my changes.
I have manually tested my changes end-to-end.
Any dependent changes have been merged and published in downstream modules.

…rsion JSON Schema allows `true` and `false` as valid boolean schemas, where `true` accepts any value and `false` rejects all values. Some MCP servers use this pattern for unconstrained fields. The schema sanitizer previously passed booleans through unchanged, causing a Pydantic ValidationError when `_ExtendedJSONSchema` tried to validate them as schema objects. Convert boolean schemas to `{"type": "object"}` as the closest approximation available in Gemini's schema model. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com> Signed-off-by: Brian Fox <878612+onematchfox@users.noreply.github.com>

gemini-code-assist · 2026-02-18T14:24:12Z

Summary of Changes

Hello @onematchfox, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a Pydantic ValidationError that occurred when the Gemini schema conversion process encountered boolean JSON schemas (e.g., true or false). These boolean schemas, which are valid in JSON Schema for representing unconstrained or rejected values, were not correctly handled, leading to crashes. The solution implemented converts these boolean schemas into a generic {"type": "object"} representation, providing a safe fallback that prevents validation errors and ensures compatibility with external systems that utilize this JSON Schema pattern.

Highlights

Problem Addressed: Resolved a Pydantic ValidationError that occurred when the Gemini schema conversion process encountered boolean JSON schemas (true or false), which are valid in JSON Schema but caused crashes due to incompatibility.
Solution Implemented: Boolean JSON schemas are now converted to a generic {"type": "object"} representation during the Gemini schema conversion, providing a safe fallback.
Impact: This change prevents validation errors and ensures compatibility with external systems (like some MCP servers) that utilize boolean schemas for unconstrained fields.
Testing: New unit tests were added to specifically cover the correct handling of both true and false boolean schemas, including a regression test for schemas within array item properties.

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Changelog

src/google/adk/tools/_gemini_schema_util.py
- Introduced logic within the _sanitize_schema_formats_for_gemini function to detect and handle boolean JSON schemas (true or false).
- Mapped boolean schemas to {"type": "object"} to ensure compatibility with Gemini's schema model and prevent Pydantic validation errors.
tests/unittests/tools/test_gemini_schema_util.py
- Added test_to_gemini_schema_boolean_true_property to verify correct handling of true boolean schemas.
- Added test_to_gemini_schema_boolean_false_property to confirm that false boolean schemas are processed without raising errors.
- Added test_to_gemini_schema_boolean_true_in_array_items_properties as a regression test for boolean true schemas within array item properties.

Activity

The author identified a Pydantic ValidationError when processing boolean JSON schemas.
A solution was implemented to convert boolean schemas to {"type": "object"}.
Unit tests were added and passed locally to validate the fix for both true and false boolean schemas, including a regression test for array item properties.
The author performed a self-review and commented the code.

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Code Review

The pull request correctly addresses the Pydantic ValidationError encountered when processing JSON schemas that use boolean values (e.g., "field": true), which is a valid pattern in JSON Schema (Draft 7+) often used by MCP servers to indicate unconstrained fields. By converting these boolean schemas to an unconstrained object schema ({"type": "object"}), the utility now handles these cases gracefully instead of crashing. The implementation is correctly placed within the recursive sanitization logic and is supported by comprehensive unit tests covering various nesting scenarios including properties and array items.

ryanaiagent · 2026-02-19T07:51:30Z

Hi @onematchfox , Thank you for your contribution! We appreciate you taking the time to submit this pull request. Your PR has been received by the team and is currently under review. We will provide feedback as soon as we have an update to share.

ryanaiagent · 2026-02-19T07:52:14Z

Hi @xuanyang15 , can you please review this. LGTM.

xuanyang15 · 2026-02-25T00:41:13Z

Started internal review process

…rsion Merge #4531 **Problem:** JSON Schema allows `true` and `false` as valid boolean schemas, where `true` accepts any value and `false` rejects all values. Some MCP servers use this pattern for unconstrained fields. E.g. [mcp-grafana](https://github.com/grafana/mcp-grafana) - see [grafana-mcp-list-tools.json](https://github.com/user-attachments/files/25392430/grafana-mcp-list-tools.json) which was obtained from `tools/list` The schema sanitizer previously passed booleans through unchanged, causing a Pydantic ValidationError when `_ExtendedJSONSchema` tried to validate them as schema objects. ``` 1 validation error for _ExtendedJSONSchema properties.data.items.properties.model Input should be a valid dictionary or object to extract fields from [type=model_attributes_type, input_value=True, input_type=bool] For further information visit https://errors.pydantic.dev/2.12/v/model_attributes_type Traceback (most recent call last): ... File "/.foo/.venv/lib/python3.13/site-packages/google/adk/runners.py", line 561, in run_async async for event in agen: yield event File "/.foo/.venv/lib/python3.13/site-packages/google/adk/runners.py", line 549, in _run_with_trace async for event in agen: yield event File "/.foo/.venv/lib/python3.13/site-packages/google/adk/runners.py", line 778, in _exec_with_plugin async for event in agen: ...<64 lines>... yield event File "/.foo/.venv/lib/python3.13/site-packages/google/adk/runners.py", line 538, in execute async for event in agen: yield event File "/.foo/.venv/lib/python3.13/site-packages/google/adk/agents/base_agent.py", line 294, in run_async async for event in agen: yield event File "/.foo/.venv/lib/python3.13/site-packages/google/adk/agents/llm_agent.py", line 468, in _run_async_impl async for event in agen: ...<5 lines>... should_pause = True File "/.foo/.venv/lib/python3.13/site-packages/google/adk/flows/llm_flows/base_llm_flow.py", line 427, in run_async async for event in agen: last_event = event yield event File "/.foo/.venv/lib/python3.13/site-packages/google/adk/flows/llm_flows/base_llm_flow.py", line 446, in _run_one_step_async async for event in agen: yield event File "/.foo/.venv/lib/python3.13/site-packages/google/adk/flows/llm_flows/base_llm_flow.py", line 578, in _preprocess_async await tool.process_llm_request( tool_context=tool_context, llm_request=llm_request ) File "/.foo/.venv/lib/python3.13/site-packages/google/adk/tools/base_tool.py", line 129, in process_llm_request llm_request.append_tools([self]) ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^ File "/.foo/.venv/lib/python3.13/site-packages/google/adk/models/llm_request.py", line 255, in append_tools declaration = tool._get_declaration() File "/.foo/.venv/lib/python3.13/site-packages/google/adk/tools/mcp_tool/mcp_tool.py", line 200, in _get_declaration parameters = _to_gemini_schema(input_schema) File "/.foo/.venv/lib/python3.13/site-packages/google/adk/tools/_gemini_schema_util.py", line 218, in _to_gemini_schema json_schema=_ExtendedJSONSchema.model_validate(sanitized_schema), ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^ File "/.foo/.venv/lib/python3.13/site-packages/pydantic/main.py", line 716, in model_validate return cls.__pydantic_validator__.validate_python( ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^ obj, ^^^^ ...<5 lines>... by_name=by_name, ^^^^^^^^^^^^^^^^ ) ^ pydantic_core._pydantic_core.ValidationError: 1 validation error for _ExtendedJSONSchema properties.data.items.properties.model Input should be a valid dictionary or object to extract fields from [type=model_attributes_type, input_value=True, input_type=bool] For further information visit https://errors.pydantic.dev/2.12/v/model_attributes_type ``` **Solution:** Convert boolean schemas to `{"type": "object"}` as the closest approximation available in Gemini's schema model. Co-authored-by: Xuan Yang <xygoogle@google.com> COPYBARA_INTEGRATE_REVIEW=#4531 from onematchfox:fix-gemini-schema-bool 383ac0c PiperOrigin-RevId: 875219362

adk-bot · 2026-02-25T18:10:57Z

Thank you @onematchfox for your contribution! 🎉

Your changes have been successfully imported and merged via Copybara in commit 3256a67.

Closing this PR as the changes are now in the main branch.

adk-bot added the tools [Component] This issue is related to tools label Feb 18, 2026

gemini-code-assist bot reviewed Feb 18, 2026

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ryanaiagent self-assigned this Feb 19, 2026

Merge branch 'main' into fix-gemini-schema-bool

383ac0c

ryanaiagent added the needs review [Status] The PR/issue is awaiting review from the maintainer label Feb 19, 2026

xuanyang15 self-assigned this Feb 23, 2026

adk-bot closed this Feb 25, 2026

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fix(tools): Handle JSON Schema boolean schemas in Gemini schema conversion#4531

fix(tools): Handle JSON Schema boolean schemas in Gemini schema conversion#4531
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onematchfox commented Feb 18, 2026

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