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redis

Redis MCP Server

Official
by redis

dbsize

Get the number of keys currently stored in the Redis database.

Instructions

Get the number of keys stored in the Redis database

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes

Implementation Reference

  • The main handler function for the 'dbsize' tool. It uses @mcp.tool() decorator to register as an MCP tool, gets a Redis connection via RedisConnectionManager, calls r.dbsize() to get the number of keys, and returns the result or an error message.
    @mcp.tool()
    async def dbsize() -> int:
        """Get the number of keys stored in the Redis database"""
        try:
            r = RedisConnectionManager.get_connection()
            return r.dbsize()
        except RedisError as e:
            return f"Error getting database size: {str(e)}"
  • The '@mcp.tool()' decorator is the registration mechanism that registers the dbsize function as an MCP tool on the FastMCP server instance.
    @mcp.tool()
  • RedisConnectionManager.get_connection() is the helper that provides the Redis connection instance used by the dbsize handler.
    class RedisConnectionManager:
        _instance: Optional[Redis] = None
    
        @classmethod
        def get_connection(cls, decode_responses=True) -> Redis:
            if cls._instance is None:
                try:
                    # Create Entra ID credential provider if configured
                    credential_provider = None
                    if is_entraid_auth_enabled():
                        try:
                            credential_provider = create_credential_provider()
                        except EntraIDAuthenticationError as e:
                            _logger.error(
                                "Failed to create Entra ID credential provider: %s", e
                            )
                            raise
    
                    if REDIS_CFG["cluster_mode"]:
                        redis_class: Type[Union[Redis, RedisCluster]] = (
                            redis.cluster.RedisCluster
                        )
                        connection_params = {
                            "host": REDIS_CFG["host"],
                            "port": REDIS_CFG["port"],
                            "username": REDIS_CFG["username"],
                            "password": REDIS_CFG["password"],
                            "ssl": REDIS_CFG["ssl"],
                            "ssl_ca_path": REDIS_CFG["ssl_ca_path"],
                            "ssl_keyfile": REDIS_CFG["ssl_keyfile"],
                            "ssl_certfile": REDIS_CFG["ssl_certfile"],
                            "ssl_cert_reqs": REDIS_CFG["ssl_cert_reqs"],
                            "ssl_ca_certs": REDIS_CFG["ssl_ca_certs"],
                            "decode_responses": decode_responses,
                            "lib_name": f"redis-py(mcp-server_v{__version__})",
                            "max_connections_per_node": 10,
                        }
    
                        # Add credential provider if available
                        if credential_provider:
                            connection_params["credential_provider"] = credential_provider
                            # Note: Azure Redis Enterprise with EntraID uses plain text connections
                            # SSL setting is controlled by REDIS_SSL environment variable
                    else:
                        redis_class: Type[Union[Redis, RedisCluster]] = redis.Redis
                        connection_params = {
                            "host": REDIS_CFG["host"],
                            "port": REDIS_CFG["port"],
                            "db": REDIS_CFG["db"],
                            "username": REDIS_CFG["username"],
                            "password": REDIS_CFG["password"],
                            "ssl": REDIS_CFG["ssl"],
                            "ssl_ca_path": REDIS_CFG["ssl_ca_path"],
                            "ssl_keyfile": REDIS_CFG["ssl_keyfile"],
                            "ssl_certfile": REDIS_CFG["ssl_certfile"],
                            "ssl_cert_reqs": REDIS_CFG["ssl_cert_reqs"],
                            "ssl_ca_certs": REDIS_CFG["ssl_ca_certs"],
                            "decode_responses": decode_responses,
                            "lib_name": f"redis-py(mcp-server_v{__version__})",
                            "max_connections": 10,
                        }
    
                        # Add credential provider if available
                        if credential_provider:
                            connection_params["credential_provider"] = credential_provider
                            # Note: Azure Redis Enterprise with EntraID uses plain text connections
                            # SSL setting is controlled by REDIS_SSL environment variable
    
                    cls._instance = redis_class(**connection_params)
    
                except redis.exceptions.ConnectionError:
                    _logger.error("Failed to connect to Redis server")
                    raise
                except redis.exceptions.AuthenticationError:
                    _logger.error("Authentication failed")
                    raise
                except redis.exceptions.TimeoutError:
                    _logger.error("Connection timed out")
                    raise
                except redis.exceptions.ResponseError as e:
                    _logger.error("Response error: %s", e)
                    raise
                except redis.exceptions.RedisError as e:
                    _logger.error("Redis error: %s", e)
                    raise
                except redis.exceptions.ClusterError as e:
                    _logger.error("Redis Cluster error: %s", e)
                    raise
                except Exception as e:
                    _logger.error("Unexpected error: %s", e)
                    raise
    
            return cls._instance
  • The load_tools() function auto-discovers and imports tool modules (including server_management.py), indirectly registering all tools decorated with @mcp.tool().
    def load_tools():
        import src.tools as tools_pkg
    
        for _, module_name, _ in pkgutil.iter_modules(tools_pkg.__path__):
            importlib.import_module(f"src.tools.{module_name}")
    
    
    # Initialize FastMCP server
    mcp = FastMCP(
        "Redis MCP Server", dependencies=["redis", "python-dotenv", "numpy", "aiohttp"]
    )
    
    # Load tools
    load_tools()
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Without annotations, the description carries the full burden. It implies a safe read operation but does not disclose any side effects, performance implications, or error cases. The behavior is universally understood but not explicitly stated.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, clear sentence with no extraneous information. It is perfectly concise and front-loaded with the action and target.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool has no parameters and an output schema exists, the description covers the essential purpose. It fully informs the agent of what the tool returns without needing additional context.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

There are no parameters, so schema coverage is 100%. The description does not add parameter details, but none are needed. Baseline score of 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb 'Get' and the resource 'number of keys stored in the Redis database', which is specific and distinct from sibling tools that deal with individual keys or other metrics.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance is provided on when to use this tool versus alternatives like 'info' or 'scan_keys'. The tool is simple, but explicit usage context would improve selection.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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