MCP Server Builder

Instructions

Implementation Reference

• src/mcp_server_builder/tools/docs.py:32-108 (handler)

  The handler function that implements the search_mcp_docs tool logic. It searches an index for the query, filters by source if specified, hydrates snippets from cache, and returns a list of relevant document results with scores.
  def search_mcp_docs( query: str, k: int = 5, source: SourceFilter = None ) -> list[dict[str, Any]]: """Search MCP protocol AND FastMCP framework documentation with ranked results. This tool searches across both documentation sources simultaneously: **MCP Protocol (modelcontextprotocol.io):** - Official protocol specification and architecture - Transports (stdio, streamable HTTP) - Tools, Resources, and Prompts primitives - Lifecycle, capabilities negotiation, and security **FastMCP Framework (gofastmcp.com):** - Python framework for building MCP servers - Decorators, type hints, and Pydantic integration - Authentication, deployment, and production patterns - Client SDK and cloud deployment Use this to find documentation for building MCP servers with either approach. Args: query: Search query string (e.g., "tool input schema", "stdio transport") k: Maximum number of results to return (default: 5) source: Optional filter - "mcp" for protocol docs only, "fastmcp" for framework docs only. If None, searches both sources. Returns: List of dictionaries containing: - url: Document URL - title: Display title - score: Relevance score (higher is better) - snippet: Contextual content preview - source: Documentation source ("mcp" or "fastmcp") """ cache.ensure_ready() index = cache.get_index() if index is None: return [] # Request more results if filtering, to ensure we get k results after filtering search_k = k * 3 if source else k results = index.search(query, k=search_k) # Apply source filter if specified if source: results = [(score, doc) for score, doc in results if _matches_source_filter(doc.uri, source)] # Limit to requested k after filtering results = results[:k] url_cache = cache.get_url_cache() # Hydrate top results with content for snippets top = results[: min(len(results), cache.SNIPPET_HYDRATE_MAX)] for _, doc in top: cached = url_cache.get(doc.uri) if cached is None or not cached.content: cache.ensure_page(doc.uri) # Build response with snippets and source return_docs: list[dict[str, Any]] = [] for score, doc in results: page = url_cache.get(doc.uri) snippet = text_processor.make_snippet(page, doc.display_title) return_docs.append( { "url": doc.uri, "title": doc.display_title, "score": round(score, 3), "snippet": snippet, "source": _get_source_from_url(doc.uri), } ) return return_docs
• src/mcp_server_builder/server.py:15-15 (registration)

  Registration of the search_mcp_docs tool on the FastMCP server instance using the mcp.tool() decorator.
  mcp.tool()(docs.search_mcp_docs)
• src/mcp_server_builder/tools/docs.py:8-8 (schema)

  Type definition for the 'source' parameter in search_mcp_docs, providing input schema validation via Literal union with None.
  SourceFilter = Literal["mcp", "fastmcp"] | None
• src/mcp_server_builder/tools/docs.py:17-22 (helper)

  Helper function to determine the documentation source (mcp or fastmcp) from a URL domain, used in filtering and result labeling.
  def _get_source_from_url(url: str) -> str: """Extract source identifier from URL domain.""" for domain, source in _DOMAIN_SOURCE_MAP.items(): if domain in url: return source return "unknown"
• src/mcp_server_builder/tools/docs.py:25-29 (helper)

  Helper function to check if a document URL matches the specified source filter.
  def _matches_source_filter(url: str, source_filter: SourceFilter) -> bool: """Check if URL matches the source filter.""" if source_filter is None: return True return _get_source_from_url(url) == source_filter