Update classes to inherit from FastMCPBaseModel instead of BaseModel (#2739)

src/fastmcp/prompts/prompt.py

@@ -68,7 +68,6 @@ class Message(pydantic.BaseModel):
         self,
         content: Any,
         role: Literal["user", "assistant"] = "user",
-        **kwargs: Any,
     ):
         """Create Message with automatic serialization.
 
@@ -88,7 +87,7 @@ class Message(pydantic.BaseModel):
             serialized = pydantic_core.to_json(content, fallback=str).decode()
             normalized_content = TextContent(type="text", text=serialized)
 
-        super().__init__(role=role, content=normalized_content, **kwargs)
+        super().__init__(role=role, content=normalized_content)
 
     def to_mcp_prompt_message(self) -> PromptMessage:
         """Convert to MCP PromptMessage."""
@@ -148,7 +147,6 @@ class PromptResult(pydantic.BaseModel):
         messages: str | list[Message],
         description: str | None = None,
         meta: dict[str, Any] | None = None,
-        **kwargs: Any,
     ):
         """Create PromptResult.
 
@@ -158,9 +156,7 @@ class PromptResult(pydantic.BaseModel):
             meta: Optional metadata about the prompt result.
         """
         normalized = self._normalize_messages(messages)
-        super().__init__(
-            messages=normalized, description=description, meta=meta, **kwargs
-        )
+        super().__init__(messages=normalized, description=description, meta=meta)
 
     @staticmethod
     def _normalize_messages(

src/fastmcp/resources/resource.py

@@ -29,9 +29,7 @@ from typing_extensions import Self
 from fastmcp.server.dependencies import without_injected_parameters
 from fastmcp.server.tasks.config import TaskConfig
 from fastmcp.utilities.components import FastMCPComponent
-from fastmcp.utilities.types import (
-    get_fn_name,
-)
+from fastmcp.utilities.types import get_fn_name
 
 
 class ResourceContent(pydantic.BaseModel):
@@ -65,7 +63,6 @@ class ResourceContent(pydantic.BaseModel):
         content: Any,
         mime_type: str | None = None,
         meta: dict[str, Any] | None = None,
-        **kwargs: Any,
     ):
         """Create ResourceContent with automatic serialization.
 
@@ -88,9 +85,7 @@ class ResourceContent(pydantic.BaseModel):
             normalized_content = pydantic_core.to_json(content, fallback=str).decode()
             mime_type = mime_type or "application/json"
 
-        super().__init__(
-            content=normalized_content, mime_type=mime_type, meta=meta, **kwargs
-        )
+        super().__init__(content=normalized_content, mime_type=mime_type, meta=meta)
 
     def to_mcp_resource_contents(
         self, uri: AnyUrl | str
@@ -162,7 +157,6 @@ class ResourceResult(pydantic.BaseModel):
         self,
         contents: str | bytes | list[ResourceContent],
         meta: dict[str, Any] | None = None,
-        **kwargs: Any,
     ):
         """Create ResourceResult.
 
@@ -171,7 +165,7 @@ class ResourceResult(pydantic.BaseModel):
             meta: Optional metadata about the resource result.
         """
         normalized = self._normalize_contents(contents)
-        super().__init__(contents=normalized, meta=meta, **kwargs)
+        super().__init__(contents=normalized, meta=meta)
 
     @staticmethod
     def _normalize_contents(

src/fastmcp/server/event_store.py

@@ -16,14 +16,14 @@ from key_value.aio.stores.memory import MemoryStore
 from mcp.server.streamable_http import EventCallback, EventId, EventMessage, StreamId
 from mcp.server.streamable_http import EventStore as SDKEventStore
 from mcp.types import JSONRPCMessage
-from pydantic import BaseModel
 
 from fastmcp.utilities.logging import get_logger
+from fastmcp.utilities.types import FastMCPBaseModel
 
 logger = get_logger(__name__)
 
 
-class EventEntry(BaseModel):
+class EventEntry(FastMCPBaseModel):
     """Stored event entry."""
 
     event_id: str
@@ -31,7 +31,7 @@ class EventEntry(BaseModel):
     message: dict | None  # JSONRPCMessage serialized to dict
 
 
-class StreamEventList(BaseModel):
+class StreamEventList(FastMCPBaseModel):
     """List of event IDs for a stream."""
 
     event_ids: list[str]

src/fastmcp/server/middleware/caching.py

@@ -14,7 +14,7 @@ from key_value.aio.wrappers.statistics import StatisticsWrapper
 from key_value.aio.wrappers.statistics.wrapper import (
     KVStoreCollectionStatistics,
 )
-from pydantic import BaseModel, Field
+from pydantic import Field
 from typing_extensions import NotRequired, Self, override
 
 from fastmcp.prompts.prompt import Message, Prompt, PromptResult
@@ -22,6 +22,7 @@ from fastmcp.resources.resource import Resource, ResourceContent, ResourceResult
 from fastmcp.server.middleware.middleware import CallNext, Middleware, MiddlewareContext
 from fastmcp.tools.tool import Tool, ToolResult
 from fastmcp.utilities.logging import get_logger
+from fastmcp.utilities.types import FastMCPBaseModel
 
 logger: Logger = get_logger(name=__name__)
 
@@ -34,7 +35,7 @@ ONE_MB_IN_BYTES = 1024 * 1024
 GLOBAL_KEY = "__global__"
 
 
-class CachableResourceContent(BaseModel):
+class CachableResourceContent(FastMCPBaseModel):
     """A wrapper for ResourceContent that can be cached."""
 
     content: str | bytes
@@ -42,7 +43,7 @@ class CachableResourceContent(BaseModel):
     meta: dict[str, Any] | None = None
 
 
-class CachableResourceResult(BaseModel):
+class CachableResourceResult(FastMCPBaseModel):
     """A wrapper for ResourceResult that can be cached."""
 
     contents: list[CachableResourceContent]
@@ -75,7 +76,7 @@ class CachableResourceResult(BaseModel):
         )
 
 
-class CachableToolResult(BaseModel):
+class CachableToolResult(FastMCPBaseModel):
     content: list[mcp.types.ContentBlock]
     structured_content: dict[str, Any] | None
     meta: dict[str, Any] | None
@@ -96,14 +97,14 @@ class CachableToolResult(BaseModel):
         )
 
 
-class CachableMessage(BaseModel):
+class CachableMessage(FastMCPBaseModel):
     """A wrapper for Message that can be cached."""
 
     role: str
     content: mcp.types.TextContent | mcp.types.EmbeddedResource
 
 
-class CachablePromptResult(BaseModel):
+class CachablePromptResult(FastMCPBaseModel):
     """A wrapper for PromptResult that can be cached."""
 
     messages: list[CachableMessage]
@@ -168,7 +169,7 @@ class GetPromptSettings(SharedMethodSettings):
     """Configuration options for Prompt-related caching."""
 
 
-class ResponseCachingStatistics(BaseModel):
+class ResponseCachingStatistics(FastMCPBaseModel):
     list_tools: KVStoreCollectionStatistics | None = Field(default=None)
     list_resources: KVStoreCollectionStatistics | None = Field(default=None)
     list_prompts: KVStoreCollectionStatistics | None = Field(default=None)

src/fastmcp/server/sampling/sampling_tool.py

@@ -7,12 +7,13 @@ from collections.abc import Callable
 from typing import Any
 
 from mcp.types import Tool as SDKTool
-from pydantic import BaseModel, ConfigDict
+from pydantic import ConfigDict
 
 from fastmcp.tools.tool import ParsedFunction
+from fastmcp.utilities.types import FastMCPBaseModel
 
 
-class SamplingTool(BaseModel):
+class SamplingTool(FastMCPBaseModel):
     """A tool that can be used during LLM sampling.
 
     SamplingTools bundle a tool's schema (name, description, parameters) with

src/fastmcp/tools/tool.py

@@ -117,9 +117,7 @@ class ToolResult(BaseModel):
                 )
 
         super().__init__(
-            content=converted_content,
-            structured_content=structured_content,
-            meta=meta,
+            content=converted_content, structured_content=structured_content, meta=meta
         )
 
     def to_mcp_result(

tests/cli/test_config.py

@@ -432,3 +432,30 @@ class TestMCPServerConfig:
             if field != "type"
         )
         assert config.deployment.transport == "http"
+
+
+class TestMCPServerConfigRoundtrip:
+    """Test that MCPServerConfig survives model_dump() -> reconstruct pattern.
+
+    This is used by the CLI to apply overrides immutably.
+    """
+
+    def test_roundtrip_preserves_schema(self):
+        """Ensure schema_ field survives dump/reconstruct cycle."""
+        config = MCPServerConfig(source=FileSystemSource(path="server.py"))
+        config_dict = config.model_dump()
+        reconstructed = MCPServerConfig(**config_dict)
+        assert reconstructed.schema_ == config.schema_
+
+    def test_roundtrip_with_all_fields(self):
+        """Full config survives dump/reconstruct."""
+        config = MCPServerConfig(
+            source=FileSystemSource(path="server.py", entrypoint="app"),
+            environment=UVEnvironment(python="3.11"),
+            deployment=Deployment(transport="http", port=8080),
+        )
+        config_dict = config.model_dump()
+        reconstructed = MCPServerConfig(**config_dict)
+        assert reconstructed.source.path == "server.py"
+        assert reconstructed.environment.python == "3.11"
+        assert reconstructed.deployment.port == 8080