Add as_proxy improvements and tests

README.md

@@ -261,7 +261,7 @@ FastMCP introduces powerful ways to structure and deploy your MCP applications.
 
 ### Proxy Servers
 
-Create a FastMCP server that acts as an intermediary for another local or remote MCP server using `FastMCP.from_client()`. This is especially useful for bridging transports (e.g., remote SSE to local Stdio) or adding a layer of logic to a server you don't control.
+Create a FastMCP server that acts as an intermediary for another local or remote MCP server using `FastMCP.as_proxy()`. This is especially useful for bridging transports (e.g., remote SSE to local Stdio) or adding a layer of logic to a server you don't control.
 
 Learn more in the [**Proxying Documentation**](https://gofastmcp.com/patterns/proxy).
 

docs/servers/composition.mdx

@@ -167,11 +167,11 @@ FastMCP automatically uses proxy mounting when the mounted server has a custom l
 
 #### Interaction with Proxy Servers
 
-When using `FastMCP.from_client()` to create a proxy server, mounting that server will always use proxy mounting:
+When using `FastMCP.as_proxy()` to create a proxy server, mounting that server will always use proxy mounting:
 
 ```python
 # Create a proxy for a remote server
-remote_proxy = FastMCP.from_client(Client("http://example.com/mcp"))
+remote_proxy = FastMCP.as_proxy(Client("http://example.com/mcp"))
 
 # Mount the proxy (always uses proxy mounting)
 main_server.mount("remote", remote_proxy)

docs/servers/fastmcp.mdx

@@ -156,7 +156,7 @@ main.mount("sub", sub)
 
 <VersionBadge version="2.0.0" />
 
-FastMCP can act as a proxy for any MCP server (local or remote) using `FastMCP.from_client`, letting you bridge transports or add a frontend to existing servers. For example, you can expose a remote SSE server locally via stdio, or vice versa.
+FastMCP can act as a proxy for any MCP server (local or remote) using `FastMCP.as_proxy`, letting you bridge transports or add a frontend to existing servers. For example, you can expose a remote SSE server locally via stdio, or vice versa.
 
 See the [Proxying Servers](/patterns/proxy) guide for details and advanced usage.
 
@@ -164,7 +164,7 @@ See the [Proxying Servers](/patterns/proxy) guide for details and advanced usage
 from fastmcp import FastMCP, Client
 
 backend = Client("http://example.com/mcp/sse")
-proxy = FastMCP.from_client(backend, name="ProxyServer")
+proxy = FastMCP.as_proxy(backend, name="ProxyServer")
 # Now use the proxy like any FastMCP server
 ```
 

docs/servers/proxy.mdx

@@ -8,7 +8,9 @@ import { VersionBadge } from '/snippets/version-badge.mdx'
 
 <VersionBadge version="2.0.0" />
 
-FastMCP provides a powerful proxying capability that allows one FastMCP server instance to act as a frontend for another MCP server (which could be remote, running on a different transport, or even another FastMCP instance). This is achieved using the `FastMCP.from_client()` class method.
+FastMCP provides a powerful proxying capability that allows one FastMCP server instance to act as a frontend for another MCP server (which could be remote, running on a different transport, or even another FastMCP instance). This is achieved using the `FastMCP.as_proxy()` class method.
+
+`as_proxy()` accepts either an existing `Client` or any argument that can be passed to a `Client` as its `transport` parameter&mdash;such as another `FastMCP` instance or a URL to a remote server.
 
 ## What is Proxying?
 
@@ -37,26 +39,23 @@ sequenceDiagram
 
 ## Creating a Proxy
 
-The easiest way to create a proxy is using the `FastMCP.from_client()` class method. This creates a standard FastMCP server that forwards requests to another MCP server.
+The easiest way to create a proxy is using the `FastMCP.as_proxy()` class method. This creates a standard FastMCP server that forwards requests to another MCP server.
 
 ```python
-from fastmcp import FastMCP, Client
+from fastmcp import FastMCP
 
-# Create a client configured to talk to the backend server
-# This could be any MCP server - remote, local, or using any transport
-backend_client = Client("backend_server.py")  # Could be "http://remote.server/sse", etc.
-
-# Create the proxy server with from_client()
-proxy_server = FastMCP.from_client(
-    backend_client,
+# Provide the backend in any form accepted by Client
+proxy_server = FastMCP.as_proxy(
+    "backend_server.py",  # Could also be a FastMCP instance or a remote URL
     name="MyProxyServer"  # Optional settings for the proxy
 )
 
-# That's it! You now have a proxy FastMCP server that can be used
-# with any transport (SSE, stdio, etc.) just like any other FastMCP server
+# Or create the Client yourself for custom configuration
+backend_client = Client("backend_server.py")
+proxy_from_client = FastMCP.as_proxy(backend_client)
 ```
 
-**How `from_client` Works:**
+**How `as_proxy` Works:**
 
 1.  It connects to the backend server using the provided client.
 2.  It discovers all the tools, resources, resource templates, and prompts available on the backend server.
@@ -72,13 +71,10 @@ Currently, proxying focuses primarily on exposing the major MCP objects (tools,
 A common use case is to bridge transports. For example, making a remote SSE server available locally via Stdio:
 
 ```python
-from fastmcp import FastMCP, Client
+from fastmcp import FastMCP
 
-# Client targeting a remote SSE server
-client = Client("http://example.com/mcp/sse")
-
-# Create a proxy server - it's just a regular FastMCP server
-proxy = FastMCP.from_client(client, name="SSE to Stdio Proxy")
+# Target a remote SSE server directly by URL
+proxy = FastMCP.as_proxy("http://example.com/mcp/sse", name="SSE to Stdio Proxy")
 
 # The proxy can now be used with any transport
 # No special handling needed - it works like any FastMCP server
@@ -89,7 +85,7 @@ proxy = FastMCP.from_client(client, name="SSE to Stdio Proxy")
 You can also proxy an in-memory `FastMCP` instance, which is useful for adjusting the configuration or behavior of a server you don't completely control.
 
 ```python
-from fastmcp import FastMCP, Client
+from fastmcp import FastMCP
 
 # Original server
 original_server = FastMCP(name="Original")
@@ -98,12 +94,9 @@ original_server = FastMCP(name="Original")
 def tool_a() -> str: 
     return "A"
 
-# To proxy an in-memory server, first create a Client to it.
-client_to_original = Client(original_server)
-
-# Create a proxy of the original server using the client.
-proxy = FastMCP.from_client(
-    client_to_original,
+# Create a proxy of the original server directly
+proxy = FastMCP.as_proxy(
+    original_server,
     name="Proxy Server"
 )
 
@@ -113,6 +106,6 @@ proxy = FastMCP.from_client(
 
 ## `FastMCPProxy` Class
 
-Internally, `FastMCP.from_client()` uses the `FastMCPProxy` class. You generally don't need to interact with this class directly, but it's available if needed.
+Internally, `FastMCP.as_proxy()` uses the `FastMCPProxy` class. You generally don't need to interact with this class directly, but it's available if needed.
 
 Using the class directly might be necessary for advanced scenarios, like subclassing `FastMCPProxy` to add custom logic before or after forwarding requests. 

examples/in_memory_proxy_example.py

@@ -3,9 +3,8 @@ This example demonstrates how to set up and use an in-memory FastMCP proxy.
 
 It illustrates the pattern:
 1. Create an original FastMCP server with some tools.
-2. Create a Client that connects to this original server (in-memory).
-3. Create a proxy FastMCP server using FastMCP.from_client(), passing it the client from step 2.
-4. Use another Client to connect to the proxy server (in-memory) and interact with the original server's tools through the proxy.
+2. Create a proxy FastMCP server using ``FastMCP.as_proxy(original_server)``.
+3. Use another Client to connect to the proxy server (in-memory) and interact with the original server's tools through the proxy.
 """
 
 import asyncio
@@ -36,24 +35,18 @@ async def main():
     original_server.add_tool(EchoService().echo)
     print(f"   -> Original Server '{original_server.name}' created.")
 
-    # 2. Client for Proxy
-    print("\nStep 2: Creating a Client to connect to the Original Server...")
-    print("          (This client will be used internally by the proxy server)")
-    client_to_original = Client(original_server)
-    print(f"   -> Client for proxy created, targeting '{original_server.name}'.")
-
-    # 3. Proxy Server Creation
-    print("\nStep 3: Creating the Proxy Server (InMemoryProxy)...")
+    # 2. Proxy Server Creation
+    print("\nStep 2: Creating the Proxy Server (InMemoryProxy)...")
     print(
-        f"          (Using FastMCP.from_client, passing it the client from Step 2 that targets '{original_server.name}')"
+        f"          (Using FastMCP.as_proxy to wrap '{original_server.name}' directly)"
     )
-    proxy_server = FastMCP.from_client(client_to_original, name="InMemoryProxy")
+    proxy_server = FastMCP.as_proxy(original_server, name="InMemoryProxy")
     print(
         f"   -> Proxy Server '{proxy_server.name}' created, proxying '{original_server.name}'."
     )
 
-    # 4. Interacting via Proxy
-    print("\nStep 4: Using a new Client to connect to the Proxy Server and interact...")
+    # 3. Interacting via Proxy
+    print("\nStep 3: Using a new Client to connect to the Proxy Server and interact...")
     async with Client(proxy_server) as final_client:
         print(f"   -> Successfully connected to proxy '{proxy_server.name}'.")
 

src/fastmcp/server/server.py

@@ -11,6 +11,7 @@ from contextlib import (
     asynccontextmanager,
 )
 from functools import partial
+from pathlib import Path
 from typing import TYPE_CHECKING, Any, Generic, Literal
 
 import anyio
@@ -60,6 +61,7 @@ from fastmcp.utilities.logging import get_logger
 
 if TYPE_CHECKING:
     from fastmcp.client import Client
+    from fastmcp.client.transports import ClientTransport
     from fastmcp.server.openapi import FastMCPOpenAPI
     from fastmcp.server.proxy import FastMCPProxy
 logger = get_logger(__name__)
@@ -1104,14 +1106,47 @@ class FastMCP(Generic[LifespanResultT]):
             openapi_spec=app.openapi(), client=client, name=name, **settings
         )
 
+    @classmethod
+    def as_proxy(
+        cls,
+        backend: Client
+        | ClientTransport
+        | FastMCP[Any]
+        | AnyUrl
+        | Path
+        | dict[str, Any]
+        | str,
+        **settings: Any,
+    ) -> FastMCPProxy:
+        """Create a FastMCP proxy server for the given backend.
+
+        The ``backend`` argument can be either an existing :class:`~fastmcp.client.Client`
+        instance or any value accepted as the ``transport`` argument of
+        :class:`~fastmcp.client.Client`. This mirrors the convenience of the
+        ``Client`` constructor.
+        """
+        from fastmcp.server.proxy import FastMCPProxy
+
+        if isinstance(backend, Client):
+            client = backend
+        else:
+            client = Client(backend)
+
+        return FastMCPProxy(client=client, **settings)
+
     @classmethod
     def from_client(cls, client: Client, **settings: Any) -> FastMCPProxy:
         """
         Create a FastMCP proxy server from a FastMCP client.
         """
-        from fastmcp.server.proxy import FastMCPProxy
+        # Deprecated since 2.4.0
+        warnings.warn(
+            "FastMCP.from_client() is deprecated; use FastMCP.as_proxy() instead.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
 
-        return FastMCPProxy(client=client, **settings)
+        return cls.as_proxy(client, **settings)
 
 
 def _validate_resource_prefix(prefix: str) -> None:

tests/server/test_import_server.py

@@ -299,7 +299,7 @@ async def test_import_with_proxy_tools():
     def get_data(query: str) -> str:
         return f"Data for query: {query}"
 
-    proxy_app = FastMCP.from_client(Client(api_app))
+    proxy_app = FastMCP.as_proxy(Client(api_app))
     await main_app.import_server("api", proxy_app)
 
     result = await main_app._mcp_call_tool("api_get_data", {"query": "test"})
@@ -323,7 +323,7 @@ async def test_import_with_proxy_prompts():
         """Example greeting prompt."""
         return f"Hello, {name} from API!"
 
-    proxy_app = FastMCP.from_client(Client(api_app))
+    proxy_app = FastMCP.as_proxy(Client(api_app))
     await main_app.import_server("api", proxy_app)
 
     result = await main_app._mcp_get_prompt("api_greeting", {"name": "World"})
@@ -351,7 +351,7 @@ async def test_import_with_proxy_resources():
             "base_url": "https://api.example.com",
         }
 
-    proxy_app = FastMCP.from_client(Client(api_app))
+    proxy_app = FastMCP.as_proxy(Client(api_app))
     await main_app.import_server("api", proxy_app)
 
     # Access the resource through the main app with the prefixed key
@@ -379,7 +379,7 @@ async def test_import_with_proxy_resource_templates():
     def create_user(name: str, email: str):
         return {"name": name, "email": email}
 
-    proxy_app = FastMCP.from_client(Client(api_app))
+    proxy_app = FastMCP.as_proxy(Client(api_app))
     await main_app.import_server("api", proxy_app)
 
     # Instantiate the template through the main app with the prefixed key

tests/server/test_mount.py

@@ -373,7 +373,7 @@ class TestProxyServer:
             return f"Data for {query}"
 
         # Create proxy server
-        proxy_server = FastMCP.from_client(
+        proxy_server = FastMCP.as_proxy(
             Client(transport=FastMCPTransport(original_server))
         )
 
@@ -396,7 +396,7 @@ class TestProxyServer:
         original_server = FastMCP("OriginalServer")
 
         # Create proxy server
-        proxy_server = FastMCP.from_client(
+        proxy_server = FastMCP.as_proxy(
             Client(transport=FastMCPTransport(original_server))
         )
 
@@ -428,7 +428,7 @@ class TestProxyServer:
             return {"api_key": "12345"}
 
         # Create proxy server
-        proxy_server = FastMCP.from_client(
+        proxy_server = FastMCP.as_proxy(
             Client(transport=FastMCPTransport(original_server))
         )
 
@@ -452,7 +452,7 @@ class TestProxyServer:
             return f"Welcome, {name}!"
 
         # Create proxy server
-        proxy_server = FastMCP.from_client(
+        proxy_server = FastMCP.as_proxy(
             Client(transport=FastMCPTransport(original_server))
         )
 
@@ -510,7 +510,7 @@ class TestAsProxyKwarg:
     async def test_as_proxy_ignored_for_proxy_mounts_default(self):
         mcp = FastMCP("Main")
         sub = FastMCP("Sub")
-        sub_proxy = FastMCP.from_client(Client(transport=FastMCPTransport(sub)))
+        sub_proxy = FastMCP.as_proxy(Client(transport=FastMCPTransport(sub)))
 
         mcp.mount("sub", sub_proxy)
 
@@ -519,7 +519,7 @@ class TestAsProxyKwarg:
     async def test_as_proxy_ignored_for_proxy_mounts_false(self):
         mcp = FastMCP("Main")
         sub = FastMCP("Sub")
-        sub_proxy = FastMCP.from_client(Client(transport=FastMCPTransport(sub)))
+        sub_proxy = FastMCP.as_proxy(Client(transport=FastMCPTransport(sub)))
 
         mcp.mount("sub", sub_proxy, as_proxy=False)
 
@@ -528,7 +528,7 @@ class TestAsProxyKwarg:
     async def test_as_proxy_ignored_for_proxy_mounts_true(self):
         mcp = FastMCP("Main")
         sub = FastMCP("Sub")
-        sub_proxy = FastMCP.from_client(Client(transport=FastMCPTransport(sub)))
+        sub_proxy = FastMCP.as_proxy(Client(transport=FastMCPTransport(sub)))
 
         mcp.mount("sub", sub_proxy, as_proxy=True)
 

tests/server/test_proxy.py

@@ -66,7 +66,7 @@ def fastmcp_server():
 @pytest.fixture
 async def proxy_server(fastmcp_server):
     """Fixture that creates a FastMCP proxy server."""
-    return FastMCP.from_client(Client(transport=FastMCPTransport(fastmcp_server)))
+    return FastMCP.as_proxy(Client(transport=FastMCPTransport(fastmcp_server)))
 
 
 async def test_create_proxy(fastmcp_server):
@@ -81,6 +81,29 @@ async def test_create_proxy(fastmcp_server):
     assert server.name == "FastMCP"
 
 
+async def test_as_proxy_with_server(fastmcp_server):
+    """FastMCP.as_proxy should accept a FastMCP instance."""
+    proxy = FastMCP.as_proxy(fastmcp_server)
+    result = await proxy._mcp_call_tool("greet", {"name": "Test"})
+    assert isinstance(result[0], mcp.types.TextContent)
+    assert result[0].text == "Hello, Test!"
+
+
+async def test_as_proxy_with_transport(fastmcp_server):
+    """FastMCP.as_proxy should accept a ClientTransport."""
+    proxy = FastMCP.as_proxy(FastMCPTransport(fastmcp_server))
+    result = await proxy._mcp_call_tool("greet", {"name": "Test"})
+    assert isinstance(result[0], mcp.types.TextContent)
+    assert result[0].text == "Hello, Test!"
+
+
+def test_as_proxy_with_url():
+    """FastMCP.as_proxy should accept a URL without connecting."""
+    proxy = FastMCP.as_proxy("http://example.com/mcp")
+    assert isinstance(proxy, FastMCPProxy)
+    assert repr(proxy.client.transport).startswith("<StreamableHttp(")
+
+
 class TestTools:
     async def test_get_tools(self, proxy_server):
         tools = await proxy_server.get_tools()

tests/test_deprecated.py

@@ -6,7 +6,7 @@ from unittest.mock import AsyncMock, patch
 import pytest
 from starlette.applications import Starlette
 
-from fastmcp import FastMCP
+from fastmcp import Client, FastMCP
 
 
 def test_fastmcp_kwargs_settings_deprecation_warning():
@@ -91,3 +91,10 @@ def test_http_app_with_sse_transport():
             w for w in recorded_warnings if issubclass(w.category, DeprecationWarning)
         ]
         assert len(deprecation_warnings) == 0
+
+
+def test_from_client_deprecation_warning():
+    """Test that FastMCP.from_client raises a deprecation warning."""
+    server = FastMCP("TestServer")
+    with pytest.warns(DeprecationWarning, match="from_client"):
+        FastMCP.from_client(Client(server))