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Rename FastMCP to MCPServer (#1951)

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Marcelo Trylesinski 2026-01-25 14:45:52 +01:00 • committed by GitHub
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@ -45,7 +45,7 @@
- [Sampling](#sampling)
- [Logging and Notifications](#logging-and-notifications)
- [Authentication](#authentication)
- [FastMCP Properties](#fastmcp-properties)
- [MCPServer Properties](#mcpserver-properties)
- [Session Properties and Methods](#session-properties-and-methods)
- [Request Context Properties](#request-context-properties)
- [Running Your Server](#running-your-server)
@ -134,18 +134,18 @@ uv run mcp
Let's create a simple MCP server that exposes a calculator tool and some data:
<!-- snippet-source examples/snippets/servers/fastmcp_quickstart.py -->
<!-- snippet-source examples/snippets/servers/mcpserver_quickstart.py -->
```python
"""FastMCP quickstart example.
"""MCPServer quickstart example.
Run from the repository root:
uv run examples/snippets/servers/fastmcp_quickstart.py
uv run examples/snippets/servers/mcpserver_quickstart.py
"""
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
# Create an MCP server
mcp = FastMCP("Demo")
mcp = MCPServer("Demo")
# Add an addition tool
@ -180,13 +180,13 @@ if __name__ == "__main__":
mcp.run(transport="streamable-http", json_response=True)
```
_Full example: [examples/snippets/servers/fastmcp_quickstart.py](https://github.com/modelcontextprotocol/python-sdk/blob/main/examples/snippets/servers/fastmcp_quickstart.py)_
_Full example: [examples/snippets/servers/mcpserver_quickstart.py](https://github.com/modelcontextprotocol/python-sdk/blob/main/examples/snippets/servers/mcpserver_quickstart.py)_
<!-- /snippet-source -->
You can install this server in [Claude Code](https://docs.claude.com/en/docs/claude-code/mcp) and interact with it right away. First, run the server:
```bash
uv run --with mcp examples/snippets/servers/fastmcp_quickstart.py
uv run --with mcp examples/snippets/servers/mcpserver_quickstart.py
```
Then add it to Claude Code:
@ -216,7 +216,7 @@ The [Model Context Protocol (MCP)](https://modelcontextprotocol.io) lets you bui
### Server
The FastMCP server is your core interface to the MCP protocol. It handles connection management, protocol compliance, and message routing:
The MCPServer server is your core interface to the MCP protocol. It handles connection management, protocol compliance, and message routing:
<!-- snippet-source examples/snippets/servers/lifespan_example.py -->
```python
@ -226,7 +226,7 @@ from collections.abc import AsyncIterator
from contextlib import asynccontextmanager
from dataclasses import dataclass
from mcp.server.fastmcp import Context, FastMCP
from mcp.server.mcpserver import Context, MCPServer
from mcp.server.session import ServerSession
@ -256,7 +256,7 @@ class AppContext:
@asynccontextmanager
async def app_lifespan(server: FastMCP) -> AsyncIterator[AppContext]:
async def app_lifespan(server: MCPServer) -> AsyncIterator[AppContext]:
"""Manage application lifecycle with type-safe context."""
# Initialize on startup
db = await Database.connect()
@ -268,7 +268,7 @@ async def app_lifespan(server: FastMCP) -> AsyncIterator[AppContext]:
# Pass lifespan to server
mcp = FastMCP("My App", lifespan=app_lifespan)
mcp = MCPServer("My App", lifespan=app_lifespan)
# Access type-safe lifespan context in tools
@ -288,9 +288,9 @@ Resources are how you expose data to LLMs. They're similar to GET endpoints in a
<!-- snippet-source examples/snippets/servers/basic_resource.py -->
```python
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
mcp = FastMCP(name="Resource Example")
mcp = MCPServer(name="Resource Example")
@mcp.resource("file://documents/{name}")
@ -319,9 +319,9 @@ Tools let LLMs take actions through your server. Unlike resources, tools are exp
<!-- snippet-source examples/snippets/servers/basic_tool.py -->
```python
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
mcp = FastMCP(name="Tool Example")
mcp = MCPServer(name="Tool Example")
@mcp.tool()
@ -340,14 +340,14 @@ def get_weather(city: str, unit: str = "celsius") -> str:
_Full example: [examples/snippets/servers/basic_tool.py](https://github.com/modelcontextprotocol/python-sdk/blob/main/examples/snippets/servers/basic_tool.py)_
<!-- /snippet-source -->
Tools can optionally receive a Context object by including a parameter with the `Context` type annotation. This context is automatically injected by the FastMCP framework and provides access to MCP capabilities:
Tools can optionally receive a Context object by including a parameter with the `Context` type annotation. This context is automatically injected by the MCPServer framework and provides access to MCP capabilities:
<!-- snippet-source examples/snippets/servers/tool_progress.py -->
```python
from mcp.server.fastmcp import Context, FastMCP
from mcp.server.mcpserver import Context, MCPServer
from mcp.server.session import ServerSession
mcp = FastMCP(name="Progress Example")
mcp = MCPServer(name="Progress Example")
@mcp.tool()
@ -395,7 +395,7 @@ validated data that clients can easily process.
**Note:** For backward compatibility, unstructured results are also
returned. Unstructured results are provided for backward compatibility
with previous versions of the MCP specification, and are quirks-compatible
with previous versions of FastMCP in the current version of the SDK.
with previous versions of MCPServer in the current version of the SDK.
**Note:** In cases where a tool function's return type annotation
causes the tool to be classified as structured _and this is undesirable_,
@ -414,10 +414,10 @@ from typing import Annotated
from pydantic import BaseModel
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
from mcp.types import CallToolResult, TextContent
mcp = FastMCP("CallToolResult Example")
mcp = MCPServer("CallToolResult Example")
class ValidationModel(BaseModel):
@ -465,9 +465,9 @@ from typing import TypedDict
from pydantic import BaseModel, Field
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
mcp = FastMCP("Structured Output Example")
mcp = MCPServer("Structured Output Example")
# Using Pydantic models for rich structured data
@ -567,10 +567,10 @@ Prompts are reusable templates that help LLMs interact with your server effectiv
<!-- snippet-source examples/snippets/servers/basic_prompt.py -->
```python
from mcp.server.fastmcp import FastMCP
from mcp.server.fastmcp.prompts import base
from mcp.server.mcpserver import MCPServer
from mcp.server.mcpserver.prompts import base
mcp = FastMCP(name="Prompt Example")
mcp = MCPServer(name="Prompt Example")
@mcp.prompt(title="Code Review")
@ -595,7 +595,7 @@ _Full example: [examples/snippets/servers/basic_prompt.py](https://github.com/mo
MCP servers can provide icons for UI display. Icons can be added to the server implementation, tools, resources, and prompts:
```python
from mcp.server.fastmcp import FastMCP, Icon
from mcp.server.mcpserver import MCPServer, Icon
# Create an icon from a file path or URL
icon = Icon(
@ -605,7 +605,7 @@ icon = Icon(
)
# Add icons to server
mcp = FastMCP(
mcp = MCPServer(
"My Server",
website_url="https://example.com",
icons=[icon]
@ -623,21 +623,21 @@ def my_resource():
return "content"
```
_Full example: [examples/fastmcp/icons_demo.py](https://github.com/modelcontextprotocol/python-sdk/blob/main/examples/fastmcp/icons_demo.py)_
_Full example: [examples/mcpserver/icons_demo.py](https://github.com/modelcontextprotocol/python-sdk/blob/main/examples/mcpserver/icons_demo.py)_
### Images
FastMCP provides an `Image` class that automatically handles image data:
MCPServer provides an `Image` class that automatically handles image data:
<!-- snippet-source examples/snippets/servers/images.py -->
```python
"""Example showing image handling with FastMCP."""
"""Example showing image handling with MCPServer."""
from PIL import Image as PILImage
from mcp.server.fastmcp import FastMCP, Image
from mcp.server.mcpserver import Image, MCPServer
mcp = FastMCP("Image Example")
mcp = MCPServer("Image Example")
@mcp.tool()
@ -660,9 +660,9 @@ The Context object is automatically injected into tool and resource functions th
To use context in a tool or resource function, add a parameter with the `Context` type annotation:
```python
from mcp.server.fastmcp import Context, FastMCP
from mcp.server.mcpserver import Context, MCPServer
mcp = FastMCP(name="Context Example")
mcp = MCPServer(name="Context Example")
@mcp.tool()
@ -678,7 +678,7 @@ The Context object provides the following capabilities:
- `ctx.request_id` - Unique ID for the current request
- `ctx.client_id` - Client ID if available
- `ctx.fastmcp` - Access to the FastMCP server instance (see [FastMCP Properties](#fastmcp-properties))
- `ctx.mcp_server` - Access to the MCPServer server instance (see [MCPServer Properties](#mcpserver-properties))
- `ctx.session` - Access to the underlying session for advanced communication (see [Session Properties and Methods](#session-properties-and-methods))
- `ctx.request_context` - Access to request-specific data and lifespan resources (see [Request Context Properties](#request-context-properties))
- `await ctx.debug(message)` - Send debug log message
@ -692,10 +692,10 @@ The Context object provides the following capabilities:
<!-- snippet-source examples/snippets/servers/tool_progress.py -->
```python
from mcp.server.fastmcp import Context, FastMCP
from mcp.server.mcpserver import Context, MCPServer
from mcp.server.session import ServerSession
mcp = FastMCP(name="Progress Example")
mcp = MCPServer(name="Progress Example")
@mcp.tool()
@ -824,12 +824,12 @@ import uuid
from pydantic import BaseModel, Field
from mcp.server.fastmcp import Context, FastMCP
from mcp.server.mcpserver import Context, MCPServer
from mcp.server.session import ServerSession
from mcp.shared.exceptions import UrlElicitationRequiredError
from mcp.types import ElicitRequestURLParams
mcp = FastMCP(name="Elicitation Example")
mcp = MCPServer(name="Elicitation Example")
class BookingPreferences(BaseModel):
@ -931,11 +931,11 @@ Tools can interact with LLMs through sampling (generating text):
<!-- snippet-source examples/snippets/servers/sampling.py -->
```python
from mcp.server.fastmcp import Context, FastMCP
from mcp.server.mcpserver import Context, MCPServer
from mcp.server.session import ServerSession
from mcp.types import SamplingMessage, TextContent
mcp = FastMCP(name="Sampling Example")
mcp = MCPServer(name="Sampling Example")
@mcp.tool()
@ -968,10 +968,10 @@ Tools can send logs and notifications through the context:
<!-- snippet-source examples/snippets/servers/notifications.py -->
```python
from mcp.server.fastmcp import Context, FastMCP
from mcp.server.mcpserver import Context, MCPServer
from mcp.server.session import ServerSession
mcp = FastMCP(name="Notifications Example")
mcp = MCPServer(name="Notifications Example")
@mcp.tool()
@ -1010,7 +1010,7 @@ from pydantic import AnyHttpUrl
from mcp.server.auth.provider import AccessToken, TokenVerifier
from mcp.server.auth.settings import AuthSettings
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
class SimpleTokenVerifier(TokenVerifier):
@ -1020,8 +1020,8 @@ class SimpleTokenVerifier(TokenVerifier):
pass # This is where you would implement actual token validation
# Create FastMCP instance as a Resource Server
mcp = FastMCP(
# Create MCPServer instance as a Resource Server
mcp = MCPServer(
"Weather Service",
# Token verifier for authentication
token_verifier=SimpleTokenVerifier(),
@ -1062,15 +1062,15 @@ For a complete example with separate Authorization Server and Resource Server im
See [TokenVerifier](src/mcp/server/auth/provider.py) for more details on implementing token validation.
### FastMCP Properties
### MCPServer Properties
The FastMCP server instance accessible via `ctx.fastmcp` provides access to server configuration and metadata:
The MCPServer server instance accessible via `ctx.mcp_server` provides access to server configuration and metadata:
- `ctx.fastmcp.name` - The server's name as defined during initialization
- `ctx.fastmcp.instructions` - Server instructions/description provided to clients
- `ctx.fastmcp.website_url` - Optional website URL for the server
- `ctx.fastmcp.icons` - Optional list of icons for UI display
- `ctx.fastmcp.settings` - Complete server configuration object containing:
- `ctx.mcp_server.name` - The server's name as defined during initialization
- `ctx.mcp_server.instructions` - Server instructions/description provided to clients
- `ctx.mcp_server.website_url` - Optional website URL for the server
- `ctx.mcp_server.icons` - Optional list of icons for UI display
- `ctx.mcp_server.settings` - Complete server configuration object containing:
- `debug` - Debug mode flag
- `log_level` - Current logging level
- `host` and `port` - Server network configuration
@ -1083,12 +1083,12 @@ The FastMCP server instance accessible via `ctx.fastmcp` provides access to serv
def server_info(ctx: Context) -> dict:
"""Get information about the current server."""
return {
"name": ctx.fastmcp.name,
"instructions": ctx.fastmcp.instructions,
"debug_mode": ctx.fastmcp.settings.debug,
"log_level": ctx.fastmcp.settings.log_level,
"host": ctx.fastmcp.settings.host,
"port": ctx.fastmcp.settings.port,
"name": ctx.mcp_server.name,
"instructions": ctx.mcp_server.instructions,
"debug_mode": ctx.mcp_server.settings.debug,
"log_level": ctx.mcp_server.settings.log_level,
"host": ctx.mcp_server.settings.host,
"port": ctx.mcp_server.settings.port,
}
```
@ -1203,9 +1203,9 @@ cd to the `examples/snippets` directory and run:
python servers/direct_execution.py
"""
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
mcp = FastMCP("My App")
mcp = MCPServer("My App")
@mcp.tool()
@ -1234,7 +1234,7 @@ python servers/direct_execution.py
uv run mcp run servers/direct_execution.py
```
Note that `uv run mcp run` or `uv run mcp dev` only supports server using FastMCP and not the low-level server variant.
Note that `uv run mcp run` or `uv run mcp dev` only supports server using MCPServer and not the low-level server variant.
### Streamable HTTP Transport
@ -1246,9 +1246,9 @@ Note that `uv run mcp run` or `uv run mcp dev` only supports server using FastMC
uv run examples/snippets/servers/streamable_config.py
"""
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
mcp = FastMCP("StatelessServer")
mcp = MCPServer("StatelessServer")
# Add a simple tool to demonstrate the server
@ -1275,7 +1275,7 @@ if __name__ == "__main__":
_Full example: [examples/snippets/servers/streamable_config.py](https://github.com/modelcontextprotocol/python-sdk/blob/main/examples/snippets/servers/streamable_config.py)_
<!-- /snippet-source -->
You can mount multiple FastMCP servers in a Starlette application:
You can mount multiple MCPServer servers in a Starlette application:
<!-- snippet-source examples/snippets/servers/streamable_starlette_mount.py -->
```python
@ -1288,10 +1288,10 @@ import contextlib
from starlette.applications import Starlette
from starlette.routing import Mount
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
# Create the Echo server
echo_mcp = FastMCP(name="EchoServer")
echo_mcp = MCPServer(name="EchoServer")
@echo_mcp.tool()
@ -1301,7 +1301,7 @@ def echo(message: str) -> str:
# Create the Math server
math_mcp = FastMCP(name="MathServer")
math_mcp = MCPServer(name="MathServer")
@math_mcp.tool()
@ -1400,10 +1400,10 @@ import contextlib
from starlette.applications import Starlette
from starlette.routing import Mount
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
# Create MCP server
mcp = FastMCP("My App")
mcp = MCPServer("My App")
@mcp.tool()
@ -1447,10 +1447,10 @@ import contextlib
from starlette.applications import Starlette
from starlette.routing import Host
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
# Create MCP server
mcp = FastMCP("MCP Host App")
mcp = MCPServer("MCP Host App")
@mcp.tool()
@ -1494,11 +1494,11 @@ import contextlib
from starlette.applications import Starlette
from starlette.routing import Mount
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
# Create multiple MCP servers
api_mcp = FastMCP("API Server")
chat_mcp = FastMCP("Chat Server")
api_mcp = MCPServer("API Server")
chat_mcp = MCPServer("Chat Server")
@api_mcp.tool()
@ -1540,7 +1540,7 @@ _Full example: [examples/snippets/servers/streamable_http_multiple_servers.py](h
<!-- snippet-source examples/snippets/servers/streamable_http_path_config.py -->
```python
"""Example showing path configuration when mounting FastMCP.
"""Example showing path configuration when mounting MCPServer.
Run from the repository root:
uvicorn examples.snippets.servers.streamable_http_path_config:app --reload
@ -1549,10 +1549,10 @@ Run from the repository root:
from starlette.applications import Starlette
from starlette.routing import Mount
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
# Create a simple FastMCP server
mcp_at_root = FastMCP("My Server")
# Create a simple MCPServer server
mcp_at_root = MCPServer("My Server")
@mcp_at_root.tool()
@ -1585,10 +1585,10 @@ You can mount the SSE server to an existing ASGI server using the `sse_app` meth
```python
from starlette.applications import Starlette
from starlette.routing import Mount, Host
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
mcp = FastMCP("My App")
mcp = MCPServer("My App")
# Mount the SSE server to the existing ASGI server
app = Starlette(
@ -1606,12 +1606,12 @@ You can also mount multiple MCP servers at different sub-paths. The SSE transpor
```python
from starlette.applications import Starlette
from starlette.routing import Mount
from mcp.server.fastmcp import FastMCP
from mcp.server.mcpserver import MCPServer
# Create multiple MCP servers
github_mcp = FastMCP("GitHub API")
browser_mcp = FastMCP("Browser")
search_mcp = FastMCP("Search")
github_mcp = MCPServer("GitHub API")
browser_mcp = MCPServer("Browser")
search_mcp = MCPServer("Search")
# Mount each server at its own sub-path
# The SSE transport automatically uses ASGI's root_path to construct
@ -2126,7 +2126,7 @@ from mcp.shared.context import RequestContext
# Create server parameters for stdio connection
server_params = StdioServerParameters(
command="uv", # Using uv to run the server
args=["run", "server", "fastmcp_quickstart", "stdio"], # We're already in snippets dir
args=["run", "server", "mcpserver_quickstart", "stdio"], # We're already in snippets dir
env={"UV_INDEX": os.environ.get("UV_INDEX", "")},
)
@ -2157,7 +2157,7 @@ async def run():
prompts = await session.list_prompts()
print(f"Available prompts: {[p.name for p in prompts.prompts]}")
# Get a prompt (greet_user prompt from fastmcp_quickstart)
# Get a prompt (greet_user prompt from mcpserver_quickstart)
if prompts.prompts:
prompt = await session.get_prompt("greet_user", arguments={"name": "Alice", "style": "friendly"})
print(f"Prompt result: {prompt.messages[0].content}")
@ -2170,13 +2170,13 @@ async def run():
tools = await session.list_tools()
print(f"Available tools: {[t.name for t in tools.tools]}")
# Read a resource (greeting resource from fastmcp_quickstart)
# Read a resource (greeting resource from mcpserver_quickstart)
resource_content = await session.read_resource("greeting://World")
content_block = resource_content.contents[0]
if isinstance(content_block, types.TextContent):
print(f"Resource content: {content_block.text}")
# Call a tool (add tool from fastmcp_quickstart)
# Call a tool (add tool from mcpserver_quickstart)
result = await session.call_tool("add", arguments={"a": 5, "b": 3})
result_unstructured = result.content[0]
if isinstance(result_unstructured, types.TextContent):
@ -2254,7 +2254,7 @@ from mcp.shared.metadata_utils import get_display_name
# Create server parameters for stdio connection
server_params = StdioServerParameters(
command="uv", # Using uv to run the server
args=["run", "server", "fastmcp_quickstart", "stdio"],
args=["run", "server", "mcpserver_quickstart", "stdio"],
env={"UV_INDEX": os.environ.get("UV_INDEX", "")},
)