fix: improve MCP tool schema types to avoid gemini tool exclusion

Author: vchomakov

src/tools/hash.py

@@ -1,3 +1,5 @@
+from typing import List, Union, Optional
+
 import numpy as np
 from redis.exceptions import RedisError
 
@@ -7,7 +9,7 @@
 
 @mcp.tool()
 async def hset(
-    name: str, key: str, value: str | int | float, expire_seconds: int = None
+    name: str, key: str, value: str | int | float, expire_seconds: Optional[int] = None
 ) -> str:
     """Set a field in a hash stored at key with an optional expiration time.
 
@@ -118,8 +120,8 @@ async def hexists(name: str, key: str) -> bool:
 
 @mcp.tool()
 async def set_vector_in_hash(
-    name: str, vector: list, vector_field: str = "vector"
-) -> bool:
+    name: str, vector: List[float], vector_field: str = "vector"
+) -> Union[bool, str]:
     """Store a vector as a field in a Redis hash.
 
     Args:

src/tools/json.py

@@ -1,24 +1,44 @@
 import json
-from typing import Union, Mapping, List, TYPE_CHECKING
+from typing import Optional
 from redis.exceptions import RedisError
+from pydantic_core import core_schema
 
 from src.common.connection import RedisConnectionManager
 from src.common.server import mcp
 
-# Define JsonType for type checking to match redis-py definition
-# Use object as runtime type to avoid issubclass() issues with Any in Python 3.10
-if TYPE_CHECKING:
-    JsonType = Union[
-        str, int, float, bool, None, Mapping[str, "JsonType"], List["JsonType"]
-    ]
-else:
-    # Use object at runtime to avoid MCP framework issubclass() issues
-    JsonType = object
+
+# Custom type that accepts any JSON value but generates a proper schema
+class JsonValue:
+    """Accepts any JSON-serializable value."""
+
+    @classmethod
+    def __get_pydantic_core_schema__(cls, _source_type, _handler):
+        """Define how Pydantic should validate this type."""
+        # Accept any value
+        return core_schema.any_schema()
+
+    @classmethod
+    def __get_pydantic_json_schema__(cls, _core_schema, _handler):
+        """Define the JSON schema for this type."""
+        # Return a schema that accepts string, number, boolean, object, array, or null
+        return {
+            "anyOf": [
+                {"type": "string"},
+                {"type": "number"},
+                {"type": "boolean"},
+                {"type": "object"},
+                {"type": "array", "items": {"type": "string"}},
+                {"type": "null"},
+            ]
+        }
 
 
 @mcp.tool()
 async def json_set(
-    name: str, path: str, value: JsonType, expire_seconds: int = None
+    name: str,
+    path: str,
+    value: JsonValue,
+    expire_seconds: Optional[int] = None,
 ) -> str:
     """Set a JSON value in Redis at a given path with an optional expiration time.
 

src/tools/list.py

@@ -1,4 +1,5 @@
 import json
+from typing import Union, List, Optional
 
 from redis.exceptions import RedisError
 from redis.typing import FieldT
@@ -8,7 +9,7 @@
 
 
 @mcp.tool()
-async def lpush(name: str, value: FieldT, expire: int = None) -> str:
+async def lpush(name: str, value: FieldT, expire: Optional[int] = None) -> str:
     """Push a value onto the left of a Redis list and optionally set an expiration time."""
     try:
         r = RedisConnectionManager.get_connection()
@@ -21,7 +22,7 @@ async def lpush(name: str, value: FieldT, expire: int = None) -> str:
 
 
 @mcp.tool()
-async def rpush(name: str, value: FieldT, expire: int = None) -> str:
+async def rpush(name: str, value: FieldT, expire: Optional[int] = None) -> str:
     """Push a value onto the right of a Redis list and optionally set an expiration time."""
     try:
         r = RedisConnectionManager.get_connection()
@@ -56,7 +57,7 @@ async def rpop(name: str) -> str:
 
 
 @mcp.tool()
-async def lrange(name: str, start: int, stop: int) -> list:
+async def lrange(name: str, start: int, stop: int) -> Union[str, List[str]]:
     """Get elements from a Redis list within a specific range.
 
     Returns:

src/tools/misc.py

@@ -1,4 +1,4 @@
-from typing import Any, Dict
+from typing import Any, Dict, Union, List
 
 from redis.exceptions import RedisError
 
@@ -100,7 +100,9 @@ async def rename(old_key: str, new_key: str) -> Dict[str, Any]:
 
 
 @mcp.tool()
-async def scan_keys(pattern: str = "*", count: int = 100, cursor: int = 0) -> dict:
+async def scan_keys(
+    pattern: str = "*", count: int = 100, cursor: int = 0
+) -> Union[str, Dict[str, Any]]:
     """
     Scan keys in the Redis database using the SCAN command (non-blocking, production-safe).
 
@@ -152,7 +154,9 @@ async def scan_keys(pattern: str = "*", count: int = 100, cursor: int = 0) -> di
 
 
 @mcp.tool()
-async def scan_all_keys(pattern: str = "*", batch_size: int = 100) -> list:
+async def scan_all_keys(
+    pattern: str = "*", batch_size: int = 100
+) -> Union[str, List[str]]:
     """
     Scan and return ALL keys matching a pattern using multiple SCAN iterations.
 

src/tools/redis_query_engine.py

@@ -1,4 +1,5 @@
 import json
+from typing import List, Optional, Union, Dict, Any
 
 import numpy as np
 from redis.commands.search.field import VectorField
@@ -102,12 +103,12 @@ async def create_vector_index_hash(
 
 @mcp.tool()
 async def vector_search_hash(
-    query_vector: list,
+    query_vector: List[float],
     index_name: str = "vector_index",
     vector_field: str = "vector",
     k: int = 5,
-    return_fields: list = None,
-) -> list:
+    return_fields: Optional[List[str]] = None,
+) -> Union[List[Dict[str, Any]], str]:
     """
     Perform a KNN vector similarity search using Redis 8 or later version on vectors stored in hash data structures.
 

src/tools/set.py

@@ -1,11 +1,13 @@
+from typing import Union, List, Optional
+
 from redis.exceptions import RedisError
 
 from src.common.connection import RedisConnectionManager
 from src.common.server import mcp
 
 
 @mcp.tool()
-async def sadd(name: str, value: str, expire_seconds: int = None) -> str:
+async def sadd(name: str, value: str, expire_seconds: Optional[int] = None) -> str:
     """Add a value to a Redis set with an optional expiration time.
 
     Args:
@@ -54,7 +56,7 @@ async def srem(name: str, value: str) -> str:
 
 
 @mcp.tool()
-async def smembers(name: str) -> list:
+async def smembers(name: str) -> Union[str, List[str]]:
     """Get all members of a Redis set.
 
     Args:

src/tools/sorted_set.py

@@ -1,11 +1,15 @@
+from typing import Optional
+
 from redis.exceptions import RedisError
 
 from src.common.connection import RedisConnectionManager
 from src.common.server import mcp
 
 
 @mcp.tool()
-async def zadd(key: str, score: float, member: str, expiration: int = None) -> str:
+async def zadd(
+    key: str, score: float, member: str, expiration: Optional[int] = None
+) -> str:
     """Add a member to a Redis sorted set with an optional expiration time.
 
     Args:

src/tools/stream.py

@@ -1,11 +1,15 @@
+from typing import Dict, Any, Optional
+
 from redis.exceptions import RedisError
 
 from src.common.connection import RedisConnectionManager
 from src.common.server import mcp
 
 
 @mcp.tool()
-async def xadd(key: str, fields: dict, expiration: int = None) -> str:
+async def xadd(
+    key: str, fields: Dict[str, Any], expiration: Optional[int] = None
+) -> str:
     """Add an entry to a Redis stream with an optional expiration time.
 
     Args:

src/tools/string.py

@@ -1,5 +1,5 @@
 import json
-from typing import Union
+from typing import Union, Optional
 
 from redis.exceptions import RedisError
 from redis import Redis
@@ -10,7 +10,9 @@
 
 @mcp.tool()
 async def set(
-    key: str, value: Union[str, bytes, int, float, dict], expiration: int = None
+    key: str,
+    value: Union[str, bytes, int, float, dict],
+    expiration: Optional[int] = None,
 ) -> str:
     """Set a Redis string value with an optional expiration time.