Single tool 'search_bm25' has a basic schema with two parameters (query, top_k) but lacks critical quality markers. The tool description is minimal (10 chars: 'Search document index using Okapi BM25.') and does not explain WHEN to use it, WHAT it returns, or any prerequisites. Parameter 'query' has a description but 'top_k' lacks one entirely. No output schema is documented, the response structure is inferred from code (returns list of {id, score} objects) but not formally declared. No error handling guidance, no pagination support despite returning lists, and no indication of result limits. The implementation is functional but falls well short of production-grade tool definition standards.

• Expand tool description to 80-150 characters explaining: 'Searches indexed documents using Okapi BM25 ranking. Returns up to top_k results ranked by relevance score. Use this to find documents matching a keyword query. Requires documents to be indexed first via index_document().'
• Add description to 'top_k' parameter: 'Maximum number of results to return (1-100, default 3). Higher values return more candidates but increase response size.'
• Document output schema in tool definition: 'Returns array of {id: string, score: number} objects sorted by relevance score descending.'
• Add parameter constraints: specify that 'query' must be non-empty and 'top_k' must be between 1 and 100.
• Implement error handling: return structured errors like 'No documents indexed. Call index_document() first.' or 'Invalid top_k: must be 1-100, got {value}'.