Updates to Proxy Tool

Author: strawgate

src/fastmcp/contrib/tool_transformer/README.md

@@ -1,30 +1,26 @@
-from fastmcp.contrib.tool_transformer.base import (
-    ToolParameterOverrideError,
-    TransformedToolError,
-)
-from fastmcp.contrib.tool_transformer.tool_transformer import transform_tool
-
-
-from fastmcp.contrib.tool_transformer.types import (
-    ExtraParameterNumber,
-    ExtraParameterString,
-    ExtraParameterBoolean,
-    ExtraToolParameterTypes,
+from fastmcp.contrib.tool_transformer.models import (
+    BooleanToolParameter,
+    FloatToolParameter,
+    IntToolParameter,
     PostToolCallHookProtocol,
     PreToolCallHookProtocol,
-    ToolParameterOverride,
+    StringToolParameter,
+    ToolOverride,
+    ToolParameter,
+    ToolParameterTypes,
 )
-
+from fastmcp.contrib.tool_transformer.tool_transformer import proxy_tool, transform_tool
 
 __all__ = [
-    "ExtraParameterBoolean",
-    "ExtraParameterNumber",
-    "ExtraParameterString",
-    "ExtraToolParameterTypes",
+    "BooleanToolParameter",
+    "FloatToolParameter",
+    "IntToolParameter",
     "PostToolCallHookProtocol",
     "PreToolCallHookProtocol",
-    "ToolParameterOverride",
-    "ToolParameterOverrideError",
-    "TransformedToolError",
+    "StringToolParameter",
+    "ToolOverride",
+    "ToolParameter",
+    "ToolParameterTypes",
+    "proxy_tool",
     "transform_tool",
 ]

src/fastmcp/contrib/tool_transformer/__init__.py

@@ -0,0 +1,26 @@
+class TransformedToolError(Exception):
+    """An error that occurs when a tool is transformed."""
+
+    def __init__(self, message: str):
+        super().__init__(message)
+
+
+class ToolParameterOverrideError(TransformedToolError):
+    """An error that occurs when a parameter override is invalid."""
+
+    def __init__(self, parameter_name: str):
+        super().__init__(f"Parameter {parameter_name} not found in tool.")
+
+
+class ToolParameterNotFoundError(TransformedToolError):
+    """An error that occurs when a parameter is not found in the schema."""
+
+    def __init__(self, parameter_name: str):
+        super().__init__(f"Parameter {parameter_name} not found in tool.")
+
+
+class ToolParameterAlreadyExistsError(TransformedToolError):
+    """An error that occurs when a parameter already exists in the schema."""
+
+    def __init__(self, parameter_name: str):
+        super().__init__(f"Parameter {parameter_name} already exists in schema.")

src/fastmcp/contrib/tool_transformer/base.py

@@ -5,10 +5,9 @@
 
 from fastmcp import FastMCP
 from fastmcp.client import Client
-from fastmcp.contrib.tool_transformer.tool_transformer import (
-    transform_tool,
-)
-from fastmcp.tools.tool_manager import ToolError
+from fastmcp.exceptions import ToolError
+
+from fastmcp.contrib.tool_transformer.tool_transformer import proxy_tool
 
 third_party_mcp_config = {
     "time": {
@@ -36,9 +35,11 @@ async def pre_call_hook(
             if tool_args.get("source_timezone") == "America/New_York":
                 raise ToolError("New Yorkers are not allowed to use this tool.")
 
-        transform_tool(
+        proxy_tool(
             proxied_tools["convert_time"],
             frontend_server,
+            name="transformed_convert_time",
+            description="Converts a time from New York to another timezone.",
             pre_call_hook=pre_call_hook,
         )
 

src/fastmcp/contrib/tool_transformer/errors.py

@@ -1,13 +1,14 @@
 """Sample code for FastMCP using InterceptingProxyTool."""
 
 import asyncio
+from pathlib import Path
 
+import yaml
 from fastmcp import FastMCP
 from fastmcp.client import Client
-from fastmcp.contrib.tool_transformer.loader import (
-    ToolOverrides,
-    transform_tools_from_server,
-)
+
+from fastmcp.contrib.tool_transformer import proxy_tool
+from fastmcp.contrib.tool_transformer.loader import overrides_from_yaml_file
 
 third_party_mcp_config = {
     "time": {
@@ -19,32 +20,36 @@
     }
 }
 
-override_config_yaml = ToolOverrides.from_yaml("""
+override_config_yaml = yaml.safe_load("""
 tools:
-  convert_time:
+- convert_time:
     description: >-
         An updated multi-line description 
         for the time tool.
     parameter_overrides:
-      source_timezone:
+        source_timezone:
         description: This field now has a description and a constant value
         constant: America/New_York
-      time:
+        time:
         description: This field now has a description and a default value
         default: "3:00"
 """)
 
 
 async def async_main():
     async with Client(third_party_mcp_config) as remote_mcp_client:
-        proxied_mcp_server = FastMCP.as_proxy(remote_mcp_client)
+        backend_server = FastMCP.as_proxy(remote_mcp_client)
+
+        backend_tools = await backend_server.get_tools()
 
         frontend_server = FastMCP("Frontend Server")
 
-        await transform_tools_from_server(
-            proxied_mcp_server,
-            frontend_server,
-            overrides=override_config_yaml,
+        tool_overrides = overrides_from_yaml_file(Path("override_config.yaml"))
+
+        proxy_tool(
+            tool=backend_tools["convert_time"],
+            server=frontend_server,
+            override=tool_overrides["convert_time"],
         )
 
         await frontend_server.run_async(transport="sse")

src/fastmcp/contrib/tool_transformer/example-hooks.py

@@ -4,10 +4,11 @@
 
 from fastmcp import FastMCP
 from fastmcp.client import Client
+
 from fastmcp.contrib.tool_transformer.tool_transformer import (
-    transform_tool,
+    proxy_tool,
 )
-from fastmcp.contrib.tool_transformer.types import ToolParameterOverride
+from fastmcp.contrib.tool_transformer.models import ToolParameter
 
 third_party_mcp_config = {
     "time": {
@@ -21,29 +22,31 @@
 
 
 async def async_main():
-    async with Client(third_party_mcp_config) as remote_mcp_client:
+    async with Client(third_party_mcp_config, timeout=30) as remote_mcp_client:
         proxied_mcp_server = FastMCP.as_proxy(remote_mcp_client)
 
         proxied_tools = await proxied_mcp_server.get_tools()
 
         frontend_server = FastMCP("Frontend Server")
 
-        transform_tool(
+        proxy_tool(
             proxied_tools["convert_time"],
-            frontend_server,
+            server=frontend_server,
             name="transformed_convert_time",
             description="Converts a time from New York to another timezone.",
-            parameter_overrides={
-                "source_timezone": ToolParameterOverride(
+            parameter_overrides=[
+                ToolParameter[str](
+                    name="source_timezone",
                     description="The timezone of the time to convert.",
                     constant="America/New_York",  # Source Timezone is now required to be America/New_York
                 ),
-                "time": ToolParameterOverride(
+                ToolParameter[str](
+                    name="time",
                     description="The time to convert. Must be in the format HH:MM. Default is 3:00.",
                     default="3:00",  # Time now defaults to 3:00
                 ),
                 # No override of the override the target_timezone parameter
-            },
+            ],
         )
 
         await frontend_server.run_async(transport="sse")