# Phase 8.11: Tool Chain Error Handling ✅ COMPLETED
**Estimated Time:** 1 day
**Dependencies:** Phase 8.1
**Status:** ✅ Complete
**Implementation Date:** 2026-01-28
**Completion Note:** All error handling components implemented, integrated, and tested with 19/19 tests passing.
## Overview
Implement comprehensive error handling for tool chains with full context (chain path, config source, validation errors).
## What This Phase Accomplishes
- `ToolChainError` with chain context
- Config validation at tool load time
- Error wrapping at each execution layer
- Include config_path and validation_errors in responses
## Files to Modify/Create
- `kiwi_mcp/core/errors.py` (extend)
- `kiwi_mcp/core/executor.py` (extend)
- `tests/core/test_tool_chain_errors.py` (new)
## Task Breakdown
1. Implement ToolChainError dataclass
2. Add error wrapping in executor
3. Add config validation at load time
4. Include full context in error responses
5. Write comprehensive tests
## Success Criteria
- [x] ToolChainError includes full context
- [x] Errors are wrapped at each layer
- [x] Config validation happens at load time
- [x] Error responses are LLM-actionable
- [x] Tests cover all error scenarios
## Related Sections
- Doc lines 3938-3950: Phase 8.11 description
- Doc lines 6128-6186: Appendix A.8 (Error Handling in Tool Chains)
