MCP Tool Selection Rules

Core principle: MCP Qdrant-Indexer tools are primary for exploring code and history. Start with MCP for exploration, debugging, or "where/why" questions; use literal search/file-open only for narrow exact-literal lookups.

Use MCP Qdrant-Indexer When

• Exploring or don't know exact strings/symbols
• Need semantic or cross-file understanding (relationships, patterns, architecture)
• Want ranked results with surrounding context, not just line hits
• Asking conceptual/architectural or "where/why" behavior questions
• Need rich context/snippets around matches

Use Literal Search/File-Open Only When

• Know exact string/function/variable or error message
• Only need to confirm existence or file/line quickly (not to understand behavior)

Grep Anti-Patterns (DON'T)

grep -r "auth" .        # → Use MCP: "authentication mechanisms"
grep -r "cache" .       # → Use MCP: "caching strategies"  
grep -r "error" .       # → Use MCP: "error handling patterns"
grep -r "database" .    # → Use MCP: "database operations"

Literal Search Patterns (DO)

grep -rn "UserAlreadyExists" .      # Specific error class
grep -rn "def authenticate_user" .  # Exact function name
grep -rn "REDIS_HOST" .             # Exact environment variable

Quick Decision Heuristic

| Question Type | Tool | |--------------|------| | "Where is X implemented?" | MCP repo_search | | "Who calls this and show code?" | MCP symbol_graph (hydrated w/ snippets) | | "Callers of callers? Multi-hop?" | MCP neo4j_graph_query (transitive_callers, depth=2) | | "What breaks if I change X?" | MCP neo4j_graph_query (impact, depth=2) | | "Circular dependencies?" | MCP neo4j_graph_query (cycles) | | "How does authentication work?" | MCP context_answer | | "High-level module overview?" | MCP info_request (with explanations) | | "Does REDIS_HOST exist?" | Literal grep | | "Why did behavior change?" | search_commits_for + change_history_for_path |

If in doubt → start with MCP