fix(agent): prevent JSON serialization errors with non-serializable direct tool parameters #498
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…ool parameters
Fixes issue where passing non-serializable objects (Agent instances, custom
classes, functions, etc.) as tool parameters would cause JSON serialization
errors during tool call recording.
Changes:
- Add parameter filtering in _record_tool_execution() to test each parameter
with json.dumps() and replace non-serializable objects with descriptive
strings like '<non-serializable: TypeName>'
- Remove unused 'messages' parameter from _record_tool_execution method
- Fix message format consistency (agent.tool.{name} vs agent.{name})
- Add comprehensive test coverage for various non-serializable object types
including Agent instances, custom classes, functions, sets, complex numbers
- Add edge case testing for nested structures and None values
- Add regression testing for normal serializable parameters
- Add testing for disabled recording scenarios
The fix maintains full functionality while preventing crashes, providing
clear error indicators instead of cryptic JSON serialization errors.
Closes strands-agents#350
yakshpradippatel
previously approved these changes
Jul 18, 2025
mkmeral
reviewed
Jul 18, 2025
- Replace manual serialization loop with json.dumps default parameter - Use __qualname__ for better type representation - Change format from <non-serializable> to <<non-serializable>> - Update tests to match new serialization format - Addresses PR feedback to simplify serialization approach
JackYPCOnline
approved these changes
Jul 18, 2025
dbschmigelski
pushed a commit
to Ketansuhaas/sdk-python
that referenced
this pull request
Jul 24, 2025
…irect tool parameters (strands-agents#498) * fix(agent): prevent JSON serialization errors with non-serializable tool parameters Fixes issue where passing non-serializable objects (Agent instances, custom classes, functions, etc.) as tool parameters would cause JSON serialization errors during tool call recording. Changes: - Add parameter filtering in _record_tool_execution() to test each parameter with json.dumps() and replace non-serializable objects with descriptive strings like '<non-serializable: TypeName>' - Remove unused 'messages' parameter from _record_tool_execution method - Fix message format consistency (agent.tool.{name} vs agent.{name}) - Add comprehensive test coverage for various non-serializable object types including Agent instances, custom classes, functions, sets, complex numbers - Add edge case testing for nested structures and None values - Add regression testing for normal serializable parameters - Add testing for disabled recording scenarios The fix maintains full functionality while preventing crashes, providing clear error indicators instead of cryptic JSON serialization errors. Closes strands-agents#350 * refactor: use json.dumps default parameter for non-serializable objects - Replace manual serialization loop with json.dumps default parameter - Use __qualname__ for better type representation - Change format from <non-serializable> to <<non-serializable>> - Update tests to match new serialization format - Addresses PR feedback to simplify serialization approach
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Description
This PR fixes a critical issue where passing non-serializable objects as tool parameters would cause JSON serialization errors during tool call recording, leading to crashes when agents tried to record their tool usage.
The Problem
When agents passed complex objects like Agent instances, custom classes, functions, or other non-JSON-serializable objects as tool parameters, the
_record_tool_execution()method would fail with cryptic JSON serialization errors, breaking the entire tool execution flow.The Solution
json.dumps()before recording<non-serializable: TypeName>Key Changes
_record_tool_execution()to handle non-serializable objectsmessagesparameter from method signatureagent.tool.{name}vsagent.{name})Related Issues
Closes #350
Documentation PR
No documentation changes needed - this is an internal bug fix that maintains existing API.
Type of Change
Bug fix
Testing
Comprehensive test suite added covering:
hatch run prepare- all pre-commit hooks passedTest Results
All existing tests pass, and 5 new test functions added:
test_agent_tool_non_serializable_parameter_filteringtest_agent_tool_multiple_non_serializable_typestest_agent_tool_serialization_edge_casestest_agent_tool_no_non_serializable_parameterstest_agent_tool_record_direct_tool_call_disabled_with_non_serializableChecklist
By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.