Add tags for all core MCP objects

src/fastmcp/prompts/base.py

@@ -3,11 +3,13 @@
 import inspect
 import json
 from collections.abc import Awaitable, Callable, Sequence
-from typing import Any, Literal
+from typing import Annotated, Any, Literal
 
 import pydantic_core
 from mcp.types import EmbeddedResource, ImageContent, TextContent
-from pydantic import BaseModel, Field, TypeAdapter, validate_call
+from pydantic import BaseModel, BeforeValidator, Field, TypeAdapter, validate_call
+
+from fastmcp.utilities.types import _convert_set_defaults
 
 CONTENT_TYPES = TextContent | ImageContent | EmbeddedResource
 
@@ -71,6 +73,9 @@ class Prompt(BaseModel):
     description: str | None = Field(
         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(
         None, description="Arguments that can be passed to the prompt"
     )
@@ -82,6 +87,7 @@ class Prompt(BaseModel):
         fn: Callable[..., PromptResult | Awaitable[PromptResult]],
         name: str | None = None,
         description: str | None = None,
+        tags: set[str] | None = None,
     ) -> "Prompt":
         """Create a Prompt from a function.
 
@@ -120,6 +126,7 @@ class Prompt(BaseModel):
             description=description or fn.__doc__ or "",
             arguments=arguments,
             fn=fn,
+            tags=tags or set(),
         )
 
     async def render(self, arguments: dict[str, Any] | None = None) -> list[Message]:

src/fastmcp/resources/base.py

@@ -6,6 +6,7 @@ from typing import Annotated
 from pydantic import (
     AnyUrl,
     BaseModel,
+    BeforeValidator,
     ConfigDict,
     Field,
     UrlConstraints,
@@ -13,6 +14,8 @@ from pydantic import (
     field_validator,
 )
 
+from fastmcp.utilities.types import _convert_set_defaults
+
 
 class Resource(BaseModel, abc.ABC):
     """Base class for all resources."""
@@ -26,6 +29,9 @@ class Resource(BaseModel, abc.ABC):
     description: str | None = Field(
         description="Description of the resource", default=None
     )
+    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/resources/resource_manager.py

@@ -53,6 +53,7 @@ class ResourceManager:
         name: str | None = None,
         description: str | None = None,
         mime_type: str | None = None,
+        tags: set[str] | None = None,
     ) -> ResourceTemplate:
         """Add a template from a function."""
         template = ResourceTemplate.from_function(
@@ -61,6 +62,7 @@ class ResourceManager:
             name=name,
             description=description,
             mime_type=mime_type,
+            tags=tags,
         )
         self._templates[template.uri_template] = template
         return template

src/fastmcp/resources/templates.py

@@ -5,11 +5,12 @@ from __future__ import annotations
 import inspect
 import re
 from collections.abc import Callable
-from typing import Any
+from typing import Annotated, Any
 
-from pydantic import BaseModel, Field, TypeAdapter, validate_call
+from pydantic import BaseModel, BeforeValidator, Field, TypeAdapter, validate_call
 
 from fastmcp.resources.types import FunctionResource, Resource
+from fastmcp.utilities.types import _convert_set_defaults
 
 
 class ResourceTemplate(BaseModel):
@@ -20,6 +21,9 @@ class ResourceTemplate(BaseModel):
     )
     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"
     )
@@ -36,6 +40,7 @@ class ResourceTemplate(BaseModel):
         name: str | None = None,
         description: str | None = None,
         mime_type: str | None = None,
+        tags: set[str] | None = None,
     ) -> ResourceTemplate:
         """Create a template from a function."""
         func_name = name or fn.__name__
@@ -55,6 +60,7 @@ class ResourceTemplate(BaseModel):
             mime_type=mime_type or "text/plain",
             fn=fn,
             parameters=parameters,
+            tags=tags or set(),
         )
 
     def matches(self, uri: str) -> dict[str, Any] | None:
@@ -80,6 +86,7 @@ class ResourceTemplate(BaseModel):
                 description=self.description,
                 mime_type=self.mime_type,
                 fn=lambda: result,  # Capture result in closure
+                tags=self.tags,
             )
         except Exception as e:
             raise ValueError(f"Error creating resource from template: {e}")

src/fastmcp/server/server.py

@@ -228,6 +228,7 @@ class FastMCP(Generic[LifespanResultT]):
         fn: AnyFunction,
         name: str | None = None,
         description: str | None = None,
+        tags: set[str] | None = None,
     ) -> None:
         """Add a tool to the server.
 
@@ -238,11 +239,15 @@ class FastMCP(Generic[LifespanResultT]):
             fn: The function to register as a tool
             name: Optional name for the tool (defaults to function name)
             description: Optional description of what the tool does
+            tags: Optional set of tags for categorizing the tool
         """
-        self._tool_manager.add_tool(fn, name=name, description=description)
+        self._tool_manager.add_tool(fn, name=name, description=description, tags=tags)
 
     def tool(
-        self, name: str | None = None, description: str | None = None
+        self,
+        name: str | None = None,
+        description: str | None = None,
+        tags: set[str] | None = None,
     ) -> Callable[[AnyFunction], AnyFunction]:
         """Decorator to register a tool.
 
@@ -253,6 +258,7 @@ class FastMCP(Generic[LifespanResultT]):
         Args:
             name: Optional name for the tool (defaults to function name)
             description: Optional description of what the tool does
+            tags: Optional set of tags for categorizing the tool
 
         Example:
             @server.tool()
@@ -277,7 +283,7 @@ class FastMCP(Generic[LifespanResultT]):
             )
 
         def decorator(fn: AnyFunction) -> AnyFunction:
-            self.add_tool(fn, name=name, description=description)
+            self.add_tool(fn, name=name, description=description, tags=tags)
             return fn
 
         return decorator
@@ -297,6 +303,7 @@ class FastMCP(Generic[LifespanResultT]):
         name: str | None = None,
         description: str | None = None,
         mime_type: str | None = None,
+        tags: set[str] | None = None,
     ) -> Callable[[AnyFunction], AnyFunction]:
         """Decorator to register a function as a resource.
 
@@ -314,6 +321,7 @@ class FastMCP(Generic[LifespanResultT]):
             name: Optional name for the resource
             description: Optional description of the resource
             mime_type: Optional MIME type for the resource
+            tags: Optional set of tags for categorizing the resource
 
         Example:
             @server.resource("resource://my-resource")
@@ -364,6 +372,7 @@ class FastMCP(Generic[LifespanResultT]):
                     name=name,
                     description=description,
                     mime_type=mime_type or "text/plain",
+                    tags=tags,
                 )
             else:
                 # Register as regular resource
@@ -373,6 +382,7 @@ class FastMCP(Generic[LifespanResultT]):
                     description=description,
                     mime_type=mime_type or "text/plain",
                     fn=fn,
+                    tags=tags or set(),  # Default to empty set if None
                 )
                 self.add_resource(resource)
             return fn
@@ -388,13 +398,17 @@ class FastMCP(Generic[LifespanResultT]):
         self._prompt_manager.add_prompt(prompt)
 
     def prompt(
-        self, name: str | None = None, description: str | None = None
+        self,
+        name: str | None = None,
+        description: str | None = None,
+        tags: set[str] | None = None,
     ) -> Callable[[AnyFunction], AnyFunction]:
         """Decorator to register a prompt.
 
         Args:
             name: Optional name for the prompt (defaults to function name)
             description: Optional description of what the prompt does
+            tags: Optional set of tags for categorizing the prompt
 
         Example:
             @server.prompt()
@@ -431,7 +445,9 @@ class FastMCP(Generic[LifespanResultT]):
             )
 
         def decorator(func: AnyFunction) -> AnyFunction:
-            prompt = Prompt.from_function(func, name=name, description=description)
+            prompt = Prompt.from_function(
+                func, name=name, description=description, tags=tags
+            )
             self.add_prompt(prompt)
             return func
 

src/fastmcp/tools/base.py

@@ -2,12 +2,13 @@ from __future__ import annotations as _annotations
 
 import inspect
 from collections.abc import Callable
-from typing import TYPE_CHECKING, Any
+from typing import TYPE_CHECKING, Annotated, Any
 
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, BeforeValidator, Field
 
 from fastmcp.exceptions import ToolError
 from fastmcp.utilities.func_metadata import FuncMetadata, func_metadata
+from fastmcp.utilities.types import _convert_set_defaults
 
 if TYPE_CHECKING:
     from mcp.server.session import ServerSessionT
@@ -31,6 +32,9 @@ class Tool(BaseModel):
     context_kwarg: str | None = Field(
         None, description="Name of the kwarg that should receive context"
     )
+    tags: Annotated[set[str], BeforeValidator(_convert_set_defaults)] = Field(
+        default_factory=set, description="Tags for the tool"
+    )
 
     @classmethod
     def from_function(
@@ -39,6 +43,7 @@ class Tool(BaseModel):
         name: str | None = None,
         description: str | None = None,
         context_kwarg: str | None = None,
+        tags: set[str] | None = None,
     ) -> Tool:
         """Create a Tool from a function."""
         from fastmcp import Context
@@ -72,6 +77,7 @@ class Tool(BaseModel):
             fn_metadata=func_arg_metadata,
             is_async=is_async,
             context_kwarg=context_kwarg,
+            tags=tags or set(),
         )
 
     async def run(

src/fastmcp/tools/tool_manager.py

@@ -37,9 +37,14 @@ class ToolManager:
         fn: Callable[..., Any],
         name: str | None = None,
         description: str | None = None,
+        tags: set[str] | None = None,
     ) -> Tool:
         """Add a tool to the server."""
-        tool = Tool.from_function(fn, name=name, description=description)
+        tool = Tool.from_function(fn, name=name, description=description, tags=tags)
+        return self._register_tool(tool)
+
+    def _register_tool(self, tool: Tool) -> Tool:
+        """Register a tool with the server."""
         existing = self._tools.get(tool.name)
         if existing:
             if self.warn_on_duplicate_tools:
@@ -86,5 +91,5 @@ class ToolManager:
             )
 
             # Store the copied tool
-            self._tools[prefixed_name] = copied_tool
+            self._register_tool(copied_tool)
             logger.debug(f"Imported tool: {name} as {prefixed_name}")

src/fastmcp/utilities/types.py

@@ -2,9 +2,21 @@
 
 import base64
 from pathlib import Path
+from typing import TypeVar
 
 from mcp.types import ImageContent
 
+T = TypeVar("T")
+
+
+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."""