SQL Server MCP

Instructions

Implementation Reference

• src/mssql_mcp/tools/databases.py:15-81 (handler)

  The handler function for the 'list_databases' tool. It queries sys.databases, filters out blocked and system databases (unless include_system=True), and returns a dict with the list of databases, current database, count, and blocked count.
  @mcp.tool() def list_databases(include_system: bool = False) -> dict[str, Any]: """List all available databases on the SQL Server. Queries sys.databases to discover accessible databases. System databases (master, tempdb, model, msdb) are excluded by default. Databases in the blocklist (MSSQL_BLOCKED_DATABASES) are always excluded. Args: include_system: If True, include system databases in the list Returns: Dictionary with: - databases: List of available database names - current_database: The currently active database - count: Number of databases returned - blocked_count: Number of databases hidden due to blocklist """ try: manager = get_connection_manager() config = manager.config blocked_databases = config.blocked_databases # Query all databases query = """ SELECT name, database_id, state_desc FROM sys.databases WHERE state_desc = 'ONLINE' ORDER BY name """ rows = manager.execute_query(query) # Filter databases databases = [] blocked_count = 0 for row in rows: db_name = row["name"] db_name_lower = db_name.lower() # Check if blocked if db_name_lower in blocked_databases: blocked_count += 1 continue # Check if system database if not include_system and db_name_lower in SYSTEM_DATABASES: continue databases.append(db_name) # Get current database current_db_query = "SELECT DB_NAME() AS current_database" current_db_result = manager.execute_query(current_db_query) current_database = current_db_result[0]["current_database"] if current_db_result else None return { "databases": databases, "current_database": current_database, "count": len(databases), "blocked_count": blocked_count, } except Exception as e: logger.error(f"Error listing databases: {e}") return {"error": str(e)}