Merge pull request #610 from jlowin/fix-tools-without-descriptions

Fix handling tools without descriptions

src/fastmcp/resources/template.py

@@ -148,7 +148,7 @@ class ResourceTemplate(BaseModel):
                     f"URI parameters {uri_params} must be a subset of the function arguments: {func_params}"
                 )
 
-        description = description or fn.__doc__ or ""
+        description = description or fn.__doc__
 
         if not inspect.isroutine(fn):
             fn = fn.__call__

src/fastmcp/tools/tool.py

@@ -36,7 +36,9 @@ class Tool(BaseModel):
 
     fn: Callable[..., Any]
     name: str = Field(description="Name of the tool")
-    description: str = Field(description="Description of what the tool does")
+    description: str | None = Field(
+        default=None, description="Description of what the tool does"
+    )
     parameters: dict[str, Any] = Field(description="JSON schema for tool parameters")
     tags: Annotated[set[str], BeforeValidator(_convert_set_defaults)] = Field(
         default_factory=set, description="Tags for the tool"
@@ -74,7 +76,7 @@ class Tool(BaseModel):
         if func_name == "<lambda>":
             raise ValueError("You must provide a name for lambda functions")
 
-        func_doc = description or fn.__doc__ or ""
+        func_doc = description or fn.__doc__
 
         # if the fn is a callable class, we need to get the __call__ method from here out
         if not inspect.isroutine(fn):

tests/server/test_proxy.py

@@ -30,6 +30,10 @@ def fastmcp_server():
         """Greet someone by name."""
         return f"Hello, {name}!"
 
+    @server.tool()
+    def tool_without_description() -> str:
+        return "Hello?"
+
     @server.tool()
     def add(a: int, b: int) -> int:
         """Add two numbers together."""
@@ -110,6 +114,11 @@ class TestTools:
         assert "greet" in tools
         assert "add" in tools
         assert "error_tool" in tools
+        assert "tool_without_description" in tools
+
+    async def test_tool_without_description(self, proxy_server):
+        tools = await proxy_server.get_tools()
+        assert tools["tool_without_description"].description is None
 
     async def test_list_tools_same_as_original(self, fastmcp_server, proxy_server):
         assert (