Files
adk-python/tests
Jaroslav Pantsjoha 34d9b53f37 feat: Enhance error messages for tool and agent not found errors
Merge https://github.com/google/adk-python/pull/3219

## Summary

Enhance error messages for tool and agent not found errors to provide actionable guidance and reduce developer debugging time from hours to minutes.

Fixes #3217

## Changes

### Modified Files

1. **`src/google/adk/flows/llm_flows/functions.py`**
   - Enhanced `_get_tool()` error message with:
     - Available tools list (formatted, truncated to 20 for readability)
     - Possible causes
     - Suggested fixes
     - Fuzzy matching suggestions

2. **`src/google/adk/agents/llm_agent.py`**
   - Enhanced `__get_agent_to_run()` error message with:
     - Available agents list (formatted, truncated to 20 for readability)
     - Timing/ordering issue explanation
     - Fuzzy matching for agent names
   - Added `_get_available_agent_names()` helper method

### New Test Files

3. **`tests/unittests/flows/llm_flows/test_functions_error_messages.py`**
   - Tests for enhanced tool not found error messages
   - Fuzzy matching validation
   - Edge cases (no close matches, empty tools dict, 100+ tools)

4. **`tests/unittests/agents/test_llm_agent_error_messages.py`**
   - Tests for enhanced agent not found error messages
   - Agent tree traversal validation
   - Fuzzy matching for agents
   - Long list truncation

## Testing Plan

### Unit Tests

```bash
pytest tests/unittests/flows/llm_flows/test_functions_error_messages.py -v
pytest tests/unittests/agents/test_llm_agent_error_messages.py -v
```

**Results**:  8/8 tests passing

```
tests/unittests/flows/llm_flows/test_functions_error_messages.py::test_tool_not_found_enhanced_error PASSED
tests/unittests/flows/llm_flows/test_functions_error_messages.py::test_tool_not_found_fuzzy_matching PASSED
tests/unittests/flows/llm_flows/test_functions_error_messages.py::test_tool_not_found_no_fuzzy_match PASSED
tests/unittests/flows/llm_flows/test_functions_error_messages.py::test_tool_not_found_truncates_long_list PASSED
tests/unittests/agents/test_llm_agent_error_messages.py::test_agent_not_found_enhanced_error PASSED
tests/unittests/agents/test_llm_agent_error_messages.py::test_agent_not_found_fuzzy_matching PASSED
tests/unittests/agents/test_llm_agent_error_messages.py::test_agent_tree_traversal PASSED
tests/unittests/agents/test_llm_agent_error_messages.py::test_agent_not_found_truncates_long_list PASSED

8 passed, 1 warning in 4.38s
```

### Example Enhanced Error Messages

#### Before (Current Error)

```
ValueError: Function get_equipment_specs is not found in the tools_dict: dict_keys(['get_equipment_details', 'query_vendor_catalog', 'score_proposals'])
```

#### After (Enhanced Error)

```
Function 'get_equipment_specs' is not found in available tools.

Available tools: get_equipment_details, query_vendor_catalog, score_proposals

Possible causes:
  1. LLM hallucinated the function name - review agent instruction clarity
  2. Tool not registered - verify agent.tools list
  3. Name mismatch - check for typos

Suggested fixes:
  - Review agent instruction to ensure tool usage is clear
  - Verify tool is included in agent.tools list
  - Check for typos in function name

Did you mean one of these?
  - get_equipment_details
```

## Community Impact

- **Addresses 3 active issues**: #2050, #2933 (12 comments), #2164
- **Reduces debugging time** from 3+ hours to < 5 minutes (validated in production multi-agent RFQ solution for recent partner nanothon initiative)
- **Improves developer experience** for new ADK users

## Implementation Details

- Uses standard library `difflib` for fuzzy matching (no new dependencies)
- Error path only (no performance impact on happy path)
- Measured performance: < 0.03ms per error
- Truncates long lists to first 20 items to prevent log overflow
- Fully backward compatible (same exception types)

## Checklist

- [x] Unit tests added and passing (8/8 tests)
- [x] Code formatted with `./autoformat.sh` (isort + pyink)
- [x] No new dependencies (uses standard library `difflib`)
- [x] Docstrings updated
- [x] Tested with Python 3.11
- [x] Issue #3217 created and linked

## Related Issues

- Fixes #3217
- Addresses #2050 - Tool verification callback request
- Addresses #2933 - How to handle "Function is not found in the tools_dict" Error
- Addresses #2164 - ValueError: {agent} not found in agent tree

---

**Note**: For production scenarios where LLM tool hallucinations occur, ADK's built-in [`ReflectAndRetryToolPlugin`](https://github.com/google/adk-python/blob/main/src/google/adk/plugins/reflect_retry_tool_plugin.py) can automatically retry failed tool calls (available since v1.16.0). This PR's enhanced error messages complement that by helping developers quickly identify and fix configuration issues during development.

Cheers, JP

Co-authored-by: Yvonne Yu <yyyu@google.com>
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/3219 from jpantsjoha:feat/better-error-messages a4df8bfb031685dce9e528d8eb7006f53447b75b
PiperOrigin-RevId: 826132579
2025-10-30 12:08:13 -07:00
..