diff --git a/src/fastmcp/server/middleware/caching.py b/src/fastmcp/server/middleware/caching.py
index 35565de36..fb61d4f96 100644
--- a/src/fastmcp/server/middleware/caching.py
+++ b/src/fastmcp/server/middleware/caching.py
@@ -1,11 +1,11 @@
 """A middleware for response caching."""
 
-import hashlib
 import json
 from collections.abc import Sequence
 from typing import Any, TypedDict, TypeVar, cast
 
 import mcp.types
+import pydantic_core
 from key_value.aio.adapters.pydantic import PydanticAdapter
 from key_value.aio.protocols.key_value import AsyncKeyValue
 from key_value.aio.stores.memory import MemoryStore
@@ -598,22 +598,19 @@ class ResponseCachingMiddleware(Middleware):
 def _make_call_tool_cache_key(msg: mcp.types.CallToolRequestParams) -> str:
     """Make a cache key for a tool call by hashing the tool name and its arguments."""
 
-    raw = f"{msg.name}:{_get_arguments_str(msg.arguments)}"
-    return hashlib.sha256(raw.encode("utf-8")).hexdigest()
+    return f"{msg.name}:{_get_arguments_str(msg.arguments)}"
 
 
 def _make_read_resource_cache_key(msg: mcp.types.ReadResourceRequestParams) -> str:
     """Make a cache key for a resource read by hashing the resource URI."""
 
-    raw = f"{msg.uri}"
-    return hashlib.sha256(raw.encode("utf-8")).hexdigest()
+    return f"{msg.uri}"
 
 
 def _make_get_prompt_cache_key(msg: mcp.types.GetPromptRequestParams) -> str:
     """Make a cache key for a prompt get by hashing the prompt name and its arguments."""
 
-    raw = f"{msg.name}:{_get_arguments_str(msg.arguments)}"
-    return hashlib.sha256(raw.encode("utf-8")).hexdigest()
+    return f"{msg.name}:{_get_arguments_str(msg.arguments)}"
 
 
 def _get_arguments_str(arguments: dict[str, Any] | None) -> str:
@@ -623,7 +620,7 @@ def _get_arguments_str(arguments: dict[str, Any] | None) -> str:
         return "null"
 
     try:
-        return json.dumps(arguments, sort_keys=True, separators=(",", ":"))
+        return pydantic_core.to_json(value=arguments, fallback=str).decode()
 
     except TypeError:
         return repr(arguments)
@@ -651,21 +648,3 @@ def _get_size_of_tool_result(value: ToolResult) -> int:
     )
 
     return content_size + structured_content_size
-
-
-# def get_size_of_one_value(value: BaseModel | ToolResult | ReadResourceContents) -> int:
-#     """Get the size of an mcp type."""
-
-#     if isinstance(value, ToolResult):
-#         return get_size_of_tool_result(value)
-#     if isinstance(value, ReadResourceContents):
-#         return len(value.content)
-#     return len(value.model_dump_json())
-
-
-# def get_size_of_value(value: CachableListTypes) -> int:
-#     """Get the size of a cache entry."""
-#     if isinstance(value, (BaseModel | ToolResult | ReadResourceContents)):
-#         return get_size_of_one_value(value)
-
-#     return sum(get_size_of_one_value(item) for item in value)
diff --git a/tests/server/middleware/test_caching.py b/tests/server/middleware/test_caching.py
index fd7701ae3..7701f2735 100644
--- a/tests/server/middleware/test_caching.py
+++ b/tests/server/middleware/test_caching.py
@@ -367,11 +367,7 @@ class TestResponseCachingMiddleware:
 
         key = _make_call_tool_cache_key(msg)
 
-        # Should be a SHA256 hash
-        assert len(key) == 64
-        assert key == snapshot(
-            "7fa3d5c7967a202457eeca0731709fd87ec98546ddaee829ee86ca54b1858c59"
-        )
+        assert key == snapshot('test_tool:{"param1":"value1","param2":42}')
 
         msg = mcp.types.ReadResourceRequestParams(
             uri=AnyUrl("https://test_uri"),
@@ -379,10 +375,7 @@ class TestResponseCachingMiddleware:
 
         key = _make_read_resource_cache_key(msg)
 
-        assert len(key) == 64
-        assert key == snapshot(
-            "e34cc47c03ed1ad54f02501d95ecc463b65646568961c97ca4b730cb274e9d42"
-        )
+        assert key == snapshot("https://test_uri/")
 
         msg = mcp.types.GetPromptRequestParams(
             name="test_prompt", arguments={"param1": "value1"}
@@ -390,10 +383,7 @@ class TestResponseCachingMiddleware:
 
         key = _make_get_prompt_cache_key(msg)
 
-        assert len(key) == 64
-        assert key == snapshot(
-            "6306ff84fd3ff247a4bd91271e9d727d7f051bba53fb2e3bf80958988c4baf57"
-        )
+        assert key == snapshot('test_prompt:{"param1":"value1"}')
 
 
 class TestResponseCachingMiddlewareIntegration: