Implementation of SEP-973

Author: pja-ant

examples/fastmcp/icons_demo.py

@@ -0,0 +1,59 @@
+"""
+FastMCP Icons Demo Server
+
+Demonstrates using icons with tools, resources, prompts, and implementation.
+"""
+
+import base64
+from pathlib import Path
+
+from mcp.server.fastmcp import FastMCP
+from mcp.types import Icon
+
+# Load the icon file and convert to data URI
+icon_path = Path(__file__).parent / "mcp.png"
+with open(icon_path, "rb") as f:
+    icon_data = base64.b64encode(f.read()).decode("utf-8")
+    icon_data_uri = f"data:image/png;base64,{icon_data}"
+
+icon_data = Icon(src=icon_data_uri, mimeType="image/png", sizes="32x32")
+
+# Create server with icons in implementation
+mcp = FastMCP(
+    "Icons Demo Server", website_url="https://https://github.com/modelcontextprotocol/python-sdk", icons=[icon_data]
+)
+
+
+@mcp.tool(icons=[icon_data])
+def demo_tool(message: str) -> str:
+    """A demo tool with an icon."""
+    return message
+
+
+@mcp.resource("demo://readme", icons=[icon_data])
+def readme_resource() -> str:
+    """A demo resource with an icon"""
+    return "This resource has an icon"
+
+
+@mcp.prompt("prompt_with_icon", icons=[icon_data])
+def prompt_with_icon(text: str) -> str:
+    """A demo prompt with an icon"""
+    return text
+
+
+@mcp.tool(
+    icons=[
+        Icon(src=icon_data_uri, mimeType="image/png", sizes="16x16"),
+        Icon(src=icon_data_uri, mimeType="image/png", sizes="32x32"),
+        Icon(src=icon_data_uri, mimeType="image/png", sizes="64x64"),
+    ]
+)
+def multi_icon_tool(action: str) -> str:
+    """A tool demonstrating multiple icons."""
+    return "multi_icon_tool"
+
+
+if __name__ == "__main__":
+    # Run the server
+    mcp.run()

examples/fastmcp/mcp.png

@@ -7,7 +7,7 @@
 import pydantic_core
 from pydantic import BaseModel, Field, TypeAdapter, validate_call
 
-from mcp.types import ContentBlock, TextContent
+from mcp.types import ContentBlock, Icon, TextContent
 
 
 class Message(BaseModel):
@@ -62,6 +62,7 @@ class Prompt(BaseModel):
     description: str | None = Field(None, description="Description of what the prompt does")
     arguments: list[PromptArgument] | None = Field(None, description="Arguments that can be passed to the prompt")
     fn: Callable[..., PromptResult | Awaitable[PromptResult]] = Field(exclude=True)
+    icons: list[Icon] | None = Field(default=None, description="Optional list of icons for this prompt")
 
     @classmethod
     def from_function(
@@ -70,6 +71,7 @@ def from_function(
         name: str | None = None,
         title: str | None = None,
         description: str | None = None,
+        icons: list[Icon] | None = None,
     ) -> "Prompt":
         """Create a Prompt from a function.
 
@@ -109,6 +111,7 @@ def from_function(
             description=description or fn.__doc__ or "",
             arguments=arguments,
             fn=fn,
+            icons=icons,
         )
 
     async def render(self, arguments: dict[str, Any] | None = None) -> list[Message]:

src/mcp/server/fastmcp/prompts/base.py

@@ -13,6 +13,8 @@
     field_validator,
 )
 
+from mcp.types import Icon
+
 
 class Resource(BaseModel, abc.ABC):
     """Base class for all resources."""
@@ -28,6 +30,7 @@ class Resource(BaseModel, abc.ABC):
         description="MIME type of the resource content",
         pattern=r"^[a-zA-Z0-9]+/[a-zA-Z0-9\-+.]+$",
     )
+    icons: list[Icon] | None = Field(default=None, description="Optional list of icons for this resource")
 
     @field_validator("name", mode="before")
     @classmethod

src/mcp/server/fastmcp/resources/base.py

@@ -78,6 +78,7 @@ async def create_resource(self, uri: str, params: dict[str, Any]) -> Resource:
                 description=self.description,
                 mime_type=self.mime_type,
                 fn=lambda: result,  # Capture result in closure
+                icons=None,  # Resource templates don't support icons
             )
         except Exception as e:
             raise ValueError(f"Error creating resource from template: {e}")

src/mcp/server/fastmcp/resources/templates.py

@@ -14,6 +14,7 @@
 from pydantic import AnyUrl, Field, ValidationInfo, validate_call
 
 from mcp.server.fastmcp.resources.base import Resource
+from mcp.types import Icon
 
 
 class TextResource(Resource):
@@ -80,6 +81,7 @@ def from_function(
         title: str | None = None,
         description: str | None = None,
         mime_type: str | None = None,
+        icons: list[Icon] | None = None,
     ) -> "FunctionResource":
         """Create a FunctionResource from a function."""
         func_name = name or fn.__name__
@@ -96,6 +98,7 @@ def from_function(
             description=description or fn.__doc__ or "",
             mime_type=mime_type or "text/plain",
             fn=fn,
+            icons=icons,
         )
 
 

src/mcp/server/fastmcp/resources/types.py

@@ -42,7 +42,7 @@
 from mcp.server.streamable_http_manager import StreamableHTTPSessionManager
 from mcp.server.transport_security import TransportSecuritySettings
 from mcp.shared.context import LifespanContextT, RequestContext, RequestT
-from mcp.types import AnyFunction, ContentBlock, GetPromptResult, ToolAnnotations
+from mcp.types import AnyFunction, ContentBlock, GetPromptResult, Icon, ToolAnnotations
 from mcp.types import Prompt as MCPPrompt
 from mcp.types import PromptArgument as MCPPromptArgument
 from mcp.types import Resource as MCPResource
@@ -123,6 +123,8 @@ def __init__(
         self,
         name: str | None = None,
         instructions: str | None = None,
+        website_url: str | None = None,
+        icons: list[Icon] | None = None,
         auth_server_provider: OAuthAuthorizationServerProvider[Any, Any, Any] | None = None,
         token_verifier: TokenVerifier | None = None,
         event_store: EventStore | None = None,
@@ -169,6 +171,8 @@ def __init__(
         self._mcp_server = MCPServer(
             name=name or "FastMCP",
             instructions=instructions,
+            website_url=website_url,
+            icons=icons,
             # TODO(Marcelo): It seems there's a type mismatch between the lifespan type from an FastMCP and Server.
             # We need to create a Lifespan type that is a generic on the server type, like Starlette does.
             lifespan=(lifespan_wrapper(self, self.settings.lifespan) if self.settings.lifespan else default_lifespan),  # type: ignore
@@ -276,6 +280,7 @@ async def list_tools(self) -> list[MCPTool]:
                 inputSchema=info.parameters,
                 outputSchema=info.output_schema,
                 annotations=info.annotations,
+                icons=info.icons,
             )
             for info in tools
         ]
@@ -307,6 +312,7 @@ async def list_resources(self) -> list[MCPResource]:
                 title=resource.title,
                 description=resource.description,
                 mimeType=resource.mime_type,
+                icons=resource.icons,
             )
             for resource in resources
         ]
@@ -344,6 +350,7 @@ def add_tool(
         title: str | None = None,
         description: str | None = None,
         annotations: ToolAnnotations | None = None,
+        icons: list[Icon] | None = None,
         structured_output: bool | None = None,
     ) -> None:
         """Add a tool to the server.
@@ -368,6 +375,7 @@ def add_tool(
             title=title,
             description=description,
             annotations=annotations,
+            icons=icons,
             structured_output=structured_output,
         )
 
@@ -377,6 +385,7 @@ def tool(
         title: str | None = None,
         description: str | None = None,
         annotations: ToolAnnotations | None = None,
+        icons: list[Icon] | None = None,
         structured_output: bool | None = None,
     ) -> Callable[[AnyFunction], AnyFunction]:
         """Decorator to register a tool.
@@ -423,6 +432,7 @@ def decorator(fn: AnyFunction) -> AnyFunction:
                 title=title,
                 description=description,
                 annotations=annotations,
+                icons=icons,
                 structured_output=structured_output,
             )
             return fn
@@ -463,6 +473,7 @@ def resource(
         title: str | None = None,
         description: str | None = None,
         mime_type: str | None = None,
+        icons: list[Icon] | None = None,
     ) -> Callable[[AnyFunction], AnyFunction]:
         """Decorator to register a function as a resource.
 
@@ -531,6 +542,7 @@ def decorator(fn: AnyFunction) -> AnyFunction:
                     title=title,
                     description=description,
                     mime_type=mime_type,
+                    # Note: Resource templates don't support icons
                 )
             else:
                 # Register as regular resource
@@ -541,6 +553,7 @@ def decorator(fn: AnyFunction) -> AnyFunction:
                     title=title,
                     description=description,
                     mime_type=mime_type,
+                    icons=icons,
                 )
                 self.add_resource(resource)
             return fn
@@ -556,7 +569,11 @@ def add_prompt(self, prompt: Prompt) -> None:
         self._prompt_manager.add_prompt(prompt)
 
     def prompt(
-        self, name: str | None = None, title: str | None = None, description: str | None = None
+        self,
+        name: str | None = None,
+        title: str | None = None,
+        description: str | None = None,
+        icons: list[Icon] | None = None,
     ) -> Callable[[AnyFunction], AnyFunction]:
         """Decorator to register a prompt.
 
@@ -600,7 +617,7 @@ async def analyze_file(path: str) -> list[Message]:
             )
 
         def decorator(func: AnyFunction) -> AnyFunction:
-            prompt = Prompt.from_function(func, name=name, title=title, description=description)
+            prompt = Prompt.from_function(func, name=name, title=title, description=description, icons=icons)
             self.add_prompt(prompt)
             return func
 
@@ -971,6 +988,7 @@ async def list_prompts(self) -> list[MCPPrompt]:
                     )
                     for arg in (prompt.arguments or [])
                 ],
+                icons=prompt.icons,
             )
             for prompt in prompts
         ]

src/mcp/server/fastmcp/server.py

@@ -10,7 +10,7 @@
 
 from mcp.server.fastmcp.exceptions import ToolError
 from mcp.server.fastmcp.utilities.func_metadata import FuncMetadata, func_metadata
-from mcp.types import ToolAnnotations
+from mcp.types import Icon, ToolAnnotations
 
 if TYPE_CHECKING:
     from mcp.server.fastmcp.server import Context
@@ -32,6 +32,7 @@ class Tool(BaseModel):
     is_async: bool = Field(description="Whether the tool is async")
     context_kwarg: str | None = Field(None, description="Name of the kwarg that should receive context")
     annotations: ToolAnnotations | None = Field(None, description="Optional annotations for the tool")
+    icons: list[Icon] | None = Field(default=None, description="Optional list of icons for this tool")
 
     @cached_property
     def output_schema(self) -> dict[str, Any] | None:
@@ -46,6 +47,7 @@ def from_function(
         description: str | None = None,
         context_kwarg: str | None = None,
         annotations: ToolAnnotations | None = None,
+        icons: list[Icon] | None = None,
         structured_output: bool | None = None,
     ) -> Tool:
         """Create a Tool from a function."""
@@ -85,6 +87,7 @@ def from_function(
             is_async=is_async,
             context_kwarg=context_kwarg,
             annotations=annotations,
+            icons=icons,
         )
 
     async def run(

src/mcp/server/fastmcp/tools/base.py

@@ -7,7 +7,7 @@
 from mcp.server.fastmcp.tools.base import Tool
 from mcp.server.fastmcp.utilities.logging import get_logger
 from mcp.shared.context import LifespanContextT, RequestT
-from mcp.types import ToolAnnotations
+from mcp.types import Icon, ToolAnnotations
 
 if TYPE_CHECKING:
     from mcp.server.fastmcp.server import Context
@@ -49,6 +49,7 @@ def add_tool(
         title: str | None = None,
         description: str | None = None,
         annotations: ToolAnnotations | None = None,
+        icons: list[Icon] | None = None,
         structured_output: bool | None = None,
     ) -> Tool:
         """Add a tool to the server."""
@@ -58,6 +59,7 @@ def add_tool(
             title=title,
             description=description,
             annotations=annotations,
+            icons=icons,
             structured_output=structured_output,
         )
         existing = self._tools.get(tool.name)

src/mcp/server/fastmcp/tools/tool_manager.py

@@ -135,6 +135,8 @@ def __init__(
         name: str,
         version: str | None = None,
         instructions: str | None = None,
+        website_url: str | None = None,
+        icons: list[types.Icon] | None = None,
         lifespan: Callable[
             [Server[LifespanResultT, RequestT]],
             AbstractAsyncContextManager[LifespanResultT],
@@ -143,6 +145,8 @@ def __init__(
         self.name = name
         self.version = version
         self.instructions = instructions
+        self.website_url = website_url
+        self.icons = icons
         self.lifespan = lifespan
         self.request_handlers: dict[type, Callable[..., Awaitable[types.ServerResult]]] = {
             types.PingRequest: _ping_handler,
@@ -176,6 +180,8 @@ def pkg_version(package: str) -> str:
                 experimental_capabilities or {},
             ),
             instructions=self.instructions,
+            website_url=self.website_url,
+            icons=self.icons,
         )
 
     def get_capabilities(