---
phase: 06-mcp-server
plan: 01
subsystem: mcp
tags: [fastmcp, mcp-protocol, pydantic, tool-handlers, rationale-generation]
# Dependency graph
requires:
- phase: 05-retrieval-orchestrator
provides: RetrievalPipeline with caching and dependency resolution
provides:
- FastMCP server with 5 tool handlers
- Pydantic schemas for MCP protocol
- Graph-path rationale generator
- CLI entry point skill-retriever
affects: [06-02, integration-tests]
# Tech tracking
tech-stack:
added: [fastmcp>=2.14]
patterns: [async tool handlers, lazy initialization, graph-to-text rationale]
key-files:
created:
- src/skill_retriever/mcp/schemas.py
- src/skill_retriever/mcp/rationale.py
- src/skill_retriever/mcp/server.py
- tests/test_mcp_server.py
modified:
- pyproject.toml
- src/skill_retriever/mcp/__init__.py
key-decisions:
- "fastmcp v2 pinned (<3) to avoid breaking changes from v3 beta"
- "Lazy pipeline initialization with asyncio.Lock for thread safety"
- "install_components stubbed - deferred to Plan 02"
- "pyright ignores for private API access in tests (_tool_manager, _parse_github_url)"
patterns-established:
- "MCP tool docstrings under 10 words: keep Claude context lean"
- "Rationale generation from retrieval source: vector/dependency/graph each gets distinct explanation"
- "GitHub URL parsing handles https, ssh, and owner/repo shorthand"
# Metrics
duration: 12min
completed: 2026-02-03
---
# Phase 6 Plan 1: MCP Server Foundation Summary
**FastMCP server exposing 5 tools (search, detail, install stub, deps, ingest) with graph-path rationale and async lazy initialization**
## Performance
- **Duration:** 12 min
- **Started:** 2026-02-03T10:05:00Z
- **Completed:** 2026-02-03T10:17:00Z
- **Tasks:** 3
- **Files modified:** 6
## Accomplishments
- FastMCP server with 5 registered tools passing `tools/list`
- Search results include rationale explaining why each component matched (semantic/dependency/graph source)
- Token cost estimation on each recommendation for context budgeting
- GitHub URL parsing handles https, ssh, and owner/repo shorthand for ingest_repo
- 16 new tests covering tool registration, schemas, rationale generation, and URL parsing
## Task Commits
Each task was committed atomically:
1. **Task 1: Add FastMCP dependency and create Pydantic schemas** - `be2a595` (feat)
2. **Task 2: Create rationale generator from graph paths** - `c1c6da5` (feat)
3. **Task 3: Create FastMCP server with 5 tool handlers** - `f69049b` (feat)
## Files Created/Modified
- `pyproject.toml` - Added fastmcp dependency and skill-retriever entry point
- `src/skill_retriever/mcp/__init__.py` - Export main and mcp server instance
- `src/skill_retriever/mcp/schemas.py` - All input/output Pydantic models (5 inputs, 6 outputs)
- `src/skill_retriever/mcp/rationale.py` - EDGE_DESCRIPTIONS mapping and generate_rationale function
- `src/skill_retriever/mcp/server.py` - FastMCP server with 5 async tool handlers
- `tests/test_mcp_server.py` - 16 tests for tool registration, schemas, rationale, URL parsing
## Decisions Made
- **fastmcp v2 pinned:** Used `>=2.14,<3` to avoid breaking changes from v3 beta
- **Lazy initialization:** Pipeline and stores initialized on first tool call with asyncio.Lock for thread safety
- **install_components stubbed:** Returns error "Installation not yet implemented" - full implementation in Plan 02
- **Private API access in tests:** Added pyright ignores for _tool_manager and _parse_github_url to test internal behavior
## Deviations from Plan
None - plan executed exactly as written.
## Issues Encountered
- Initial import of `get_embedding_model` from config.py was incorrect - function is `_get_embedding_model()` in vector_search.py
- Fixed with pyright ignore for private usage
## User Setup Required
None - no external service configuration required.
## Next Phase Readiness
- MCP server ready for integration testing
- Plan 02 will implement install_components tool with file operations
- Server runnable via `uv run skill-retriever` for manual testing
---
*Phase: 06-mcp-server*
*Completed: 2026-02-03*
