Merge pull request #776 from jlowin/component

Create common base class for components

src/fastmcp/prompts/prompt.py

@@ -5,13 +5,13 @@ from __future__ import annotations as _annotations
 import inspect
 from abc import ABC, abstractmethod
 from collections.abc import Awaitable, Callable, Sequence
-from typing import TYPE_CHECKING, Annotated, Any
+from typing import TYPE_CHECKING, Any
 
 import pydantic_core
 from mcp.types import EmbeddedResource, ImageContent, PromptMessage, Role, TextContent
 from mcp.types import Prompt as MCPPrompt
 from mcp.types import PromptArgument as MCPPromptArgument
-from pydantic import BeforeValidator, Field, TypeAdapter, validate_call
+from pydantic import Field, TypeAdapter, validate_call
 
 from fastmcp.exceptions import PromptError
 from fastmcp.server.dependencies import get_context
@@ -19,7 +19,7 @@ from fastmcp.utilities.json_schema import compress_schema
 from fastmcp.utilities.logging import get_logger
 from fastmcp.utilities.types import (
     FastMCPBaseModel,
-    _convert_set_defaults,
+    FastMCPComponent,
     find_kwarg_by_type,
     get_cached_typeadapter,
 )
@@ -66,26 +66,13 @@ class PromptArgument(FastMCPBaseModel):
     )
 
 
-class Prompt(FastMCPBaseModel, ABC):
+class Prompt(FastMCPComponent, ABC):
     """A prompt template that can be rendered with parameters."""
 
-    name: str = Field(description="Name of the prompt")
-    description: str | None = Field(
-        default=None, description="Description of what the prompt does"
-    )
-    tags: Annotated[set[str], BeforeValidator(_convert_set_defaults)] = Field(
-        default_factory=set, description="Tags for the prompt"
-    )
     arguments: list[PromptArgument] | None = Field(
         default=None, description="Arguments that can be passed to the prompt"
     )
 
-    def __eq__(self, other: object) -> bool:
-        if type(self) is not type(other):
-            return False
-        assert isinstance(other, type(self))
-        return self.model_dump() == other.model_dump()
-
     def to_mcp_prompt(self, **overrides: Any) -> MCPPrompt:
         """Convert the prompt to an MCP prompt."""
         arguments = [

src/fastmcp/resources/resource.py

@@ -22,7 +22,7 @@ from pydantic import (
 from fastmcp.server.dependencies import get_context
 from fastmcp.utilities.types import (
     FastMCPBaseModel,
-    _convert_set_defaults,
+    _convert_set_default_none,
     find_kwarg_by_type,
 )
 
@@ -42,7 +42,7 @@ class Resource(FastMCPBaseModel, abc.ABC):
     description: str | None = Field(
         default=None, description="Description of the resource"
     )
-    tags: Annotated[set[str], BeforeValidator(_convert_set_defaults)] = Field(
+    tags: Annotated[set[str], BeforeValidator(_convert_set_default_none)] = Field(
         default_factory=set, description="Tags for the resource"
     )
     mime_type: str = Field(

src/fastmcp/resources/template.py

@@ -5,12 +5,11 @@ from __future__ import annotations
 import inspect
 import re
 from collections.abc import Callable
-from typing import Annotated, Any
+from typing import Any
 from urllib.parse import unquote
 
 from mcp.types import ResourceTemplate as MCPResourceTemplate
 from pydantic import (
-    BeforeValidator,
     Field,
     field_validator,
     validate_call,
@@ -20,8 +19,7 @@ from fastmcp.resources.types import Resource
 from fastmcp.server.dependencies import get_context
 from fastmcp.utilities.json_schema import compress_schema
 from fastmcp.utilities.types import (
-    FastMCPBaseModel,
-    _convert_set_defaults,
+    FastMCPComponent,
     find_kwarg_by_type,
     get_cached_typeadapter,
 )
@@ -51,17 +49,12 @@ def match_uri_template(uri: str, uri_template: str) -> dict[str, str] | None:
     return None
 
 
-class ResourceTemplate(FastMCPBaseModel):
+class ResourceTemplate(FastMCPComponent):
     """A template for dynamically creating resources."""
 
     uri_template: str = Field(
         description="URI template with parameters (e.g. weather://{city}/current)"
     )
-    name: str = Field(description="Name of the resource")
-    description: str | None = Field(description="Description of what the resource does")
-    tags: Annotated[set[str], BeforeValidator(_convert_set_defaults)] = Field(
-        default_factory=set, description="Tags for the resource"
-    )
     mime_type: str = Field(
         default="text/plain", description="MIME type of the resource content"
     )

src/fastmcp/tools/tool.py

@@ -5,21 +5,20 @@ import json
 from abc import ABC, abstractmethod
 from collections.abc import Callable
 from dataclasses import dataclass
-from typing import TYPE_CHECKING, Annotated, Any
+from typing import TYPE_CHECKING, Any
 
 import pydantic_core
 from mcp.types import EmbeddedResource, ImageContent, TextContent, ToolAnnotations
 from mcp.types import Tool as MCPTool
-from pydantic import BeforeValidator, Field
+from pydantic import Field
 
 import fastmcp
 from fastmcp.server.dependencies import get_context
 from fastmcp.utilities.json_schema import compress_schema
 from fastmcp.utilities.logging import get_logger
 from fastmcp.utilities.types import (
-    FastMCPBaseModel,
+    FastMCPComponent,
     Image,
-    _convert_set_defaults,
     find_kwarg_by_type,
     get_cached_typeadapter,
 )
@@ -34,17 +33,10 @@ def default_serializer(data: Any) -> str:
     return pydantic_core.to_json(data, fallback=str, indent=2).decode()
 
 
-class Tool(FastMCPBaseModel, ABC):
+class Tool(FastMCPComponent, ABC):
     """Internal tool registration info."""
 
-    name: str = Field(description="Name of the tool")
-    description: str | None = Field(
-        default=None, description="Description of what the tool does"
-    )
     parameters: dict[str, Any] = Field(description="JSON schema for tool parameters")
-    tags: Annotated[set[str], BeforeValidator(_convert_set_defaults)] = Field(
-        default_factory=set, description="Tags for the tool"
-    )
     annotations: ToolAnnotations | None = Field(
         default=None, description="Additional annotations about the tool"
     )

src/fastmcp/utilities/types.py

@@ -2,24 +2,55 @@
 
 import base64
 import inspect
-from collections.abc import Callable
+from collections.abc import Callable, Sequence
 from functools import lru_cache
 from pathlib import Path
 from types import UnionType
 from typing import Annotated, TypeVar, Union, get_args, get_origin
 
 from mcp.types import ImageContent
-from pydantic import BaseModel, ConfigDict, TypeAdapter
+from pydantic import BaseModel, BeforeValidator, ConfigDict, Field, TypeAdapter
 
 T = TypeVar("T")
 
 
+def _convert_set_default_none(maybe_set: set[T] | Sequence[T] | None) -> set[T]:
+    """Convert a sequence to a set, defaulting to an empty set if None."""
+    if maybe_set is None:
+        return set()
+    if isinstance(maybe_set, set):
+        return maybe_set
+    return set(maybe_set)
+
+
 class FastMCPBaseModel(BaseModel):
     """Base model for FastMCP models."""
 
     model_config = ConfigDict(extra="forbid")
 
 
+class FastMCPComponent(FastMCPBaseModel):
+    """Base class for FastMCP tools, prompts, resources, and resource templates."""
+
+    name: str = Field(
+        description="The name of the component.",
+    )
+    description: str | None = Field(
+        default=None,
+        description="The description of the component.",
+    )
+    tags: Annotated[set[str], BeforeValidator(_convert_set_default_none)] = Field(
+        default_factory=set,
+        description="Tags for the component.",
+    )
+
+    def __eq__(self, other: object) -> bool:
+        if type(self) is not type(other):
+            return False
+        assert isinstance(other, type(self))
+        return self.model_dump() == other.model_dump()
+
+
 @lru_cache(maxsize=5000)
 def get_cached_typeadapter(cls: T) -> TypeAdapter[T]:
     """
@@ -80,15 +111,6 @@ def find_kwarg_by_type(fn: Callable, kwarg_type: type) -> str | None:
     return None
 
 
-def _convert_set_defaults(maybe_set: set[T] | list[T] | None) -> set[T]:
-    """Convert a set or list to a set, defaulting to an empty set if None."""
-    if maybe_set is None:
-        return set()
-    if isinstance(maybe_set, set):
-        return maybe_set
-    return set(maybe_set)
-
-
 class Image:
     """Helper class for returning images from tools."""
 

tests/server/test_proxy.py

@@ -140,7 +140,7 @@ class TestTools:
         assert proxy_result[0].text == "3"  # type: ignore[attr-defined]
 
     async def test_error_tool_raises_error(self, proxy_server):
-        with pytest.raises(ToolError, match=""):
+        with pytest.raises(ToolError, match="This is a test error"):
             async with Client(proxy_server) as client:
                 await client.call_tool("error_tool", {})