diff --git a/libs/langchain/langchain/tools/base.py b/libs/langchain/langchain/tools/base.py
index 7c24c01b3ae..5d59f7959bf 100644
--- a/libs/langchain/langchain/tools/base.py
+++ b/libs/langchain/langchain/tools/base.py
@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 import asyncio
+import inspect
 import warnings
 from abc import abstractmethod
 from functools import partial
@@ -437,7 +438,7 @@ class Tool(BaseTool):
     """Tool that takes in function or coroutine directly."""
 
     description: str = ""
-    func: Callable[..., str]
+    func: Optional[Callable[..., str]]
     """The function to run when the tool is called."""
     coroutine: Optional[Callable[..., Awaitable[str]]] = None
     """The asynchronous version of the function."""
@@ -488,16 +489,18 @@ class Tool(BaseTool):
         **kwargs: Any,
     ) -> Any:
         """Use the tool."""
-        new_argument_supported = signature(self.func).parameters.get("callbacks")
-        return (
-            self.func(
-                *args,
-                callbacks=run_manager.get_child() if run_manager else None,
-                **kwargs,
+        if self.func:
+            new_argument_supported = signature(self.func).parameters.get("callbacks")
+            return (
+                self.func(
+                    *args,
+                    callbacks=run_manager.get_child() if run_manager else None,
+                    **kwargs,
+                )
+                if new_argument_supported
+                else self.func(*args, **kwargs)
             )
-            if new_argument_supported
-            else self.func(*args, **kwargs)
-        )
+        raise NotImplementedError("Tool does not support sync")
 
     async def _arun(
         self,
@@ -523,7 +526,7 @@ class Tool(BaseTool):
 
     # TODO: this is for backwards compatibility, remove in future
     def __init__(
-        self, name: str, func: Callable, description: str, **kwargs: Any
+        self, name: str, func: Optional[Callable], description: str, **kwargs: Any
     ) -> None:
         """Initialize tool."""
         super(Tool, self).__init__(
@@ -533,17 +536,23 @@ class Tool(BaseTool):
     @classmethod
     def from_function(
         cls,
-        func: Callable,
+        func: Optional[Callable],
         name: str,  # We keep these required to support backwards compatibility
         description: str,
         return_direct: bool = False,
         args_schema: Optional[Type[BaseModel]] = None,
+        coroutine: Optional[
+            Callable[..., Awaitable[Any]]
+        ] = None,  # This is last for compatibility, but should be after func
         **kwargs: Any,
     ) -> Tool:
         """Initialize tool from a function."""
+        if func is None and coroutine is None:
+            raise ValueError("Function and/or coroutine must be provided")
         return cls(
             name=name,
             func=func,
+            coroutine=coroutine,
             description=description,
             return_direct=return_direct,
             args_schema=args_schema,
@@ -557,7 +566,7 @@ class StructuredTool(BaseTool):
     description: str = ""
     args_schema: Type[BaseModel] = Field(..., description="The tool schema.")
     """The input arguments' schema."""
-    func: Callable[..., Any]
+    func: Optional[Callable[..., Any]]
     """The function to run when the tool is called."""
     coroutine: Optional[Callable[..., Awaitable[Any]]] = None
     """The asynchronous version of the function."""
@@ -592,16 +601,18 @@ class StructuredTool(BaseTool):
         **kwargs: Any,
     ) -> Any:
         """Use the tool."""
-        new_argument_supported = signature(self.func).parameters.get("callbacks")
-        return (
-            self.func(
-                *args,
-                callbacks=run_manager.get_child() if run_manager else None,
-                **kwargs,
+        if self.func:
+            new_argument_supported = signature(self.func).parameters.get("callbacks")
+            return (
+                self.func(
+                    *args,
+                    callbacks=run_manager.get_child() if run_manager else None,
+                    **kwargs,
+                )
+                if new_argument_supported
+                else self.func(*args, **kwargs)
             )
-            if new_argument_supported
-            else self.func(*args, **kwargs)
-        )
+        raise NotImplementedError("Tool does not support sync")
 
     async def _arun(
         self,
@@ -628,7 +639,8 @@ class StructuredTool(BaseTool):
     @classmethod
     def from_function(
         cls,
-        func: Callable,
+        func: Optional[Callable] = None,
+        coroutine: Optional[Callable[..., Awaitable[Any]]] = None,
         name: Optional[str] = None,
         description: Optional[str] = None,
         return_direct: bool = False,
@@ -642,6 +654,7 @@ class StructuredTool(BaseTool):
 
         Args:
             func: The function from which to create a tool
+            coroutine: The async function from which to create a tool
             name: The name of the tool. Defaults to the function name
             description: The description of the tool. Defaults to the function docstring
             return_direct: Whether to return the result directly or as a callback
@@ -662,21 +675,31 @@ class StructuredTool(BaseTool):
                 tool = StructuredTool.from_function(add)
                 tool.run(1, 2) # 3
         """
-        name = name or func.__name__
-        description = description or func.__doc__
-        assert (
-            description is not None
-        ), "Function must have a docstring if description not provided."
+
+        if func is not None:
+            source_function = func
+        elif coroutine is not None:
+            source_function = coroutine
+        else:
+            raise ValueError("Function and/or coroutine must be provided")
+        name = name or source_function.__name__
+        description = description or source_function.__doc__
+        if description is None:
+            raise ValueError(
+                "Function must have a docstring if description not provided."
+            )
 
         # Description example:
         # search_api(query: str) - Searches the API for the query.
-        description = f"{name}{signature(func)} - {description.strip()}"
+        sig = signature(source_function)
+        description = f"{name}{sig} - {description.strip()}"
         _args_schema = args_schema
         if _args_schema is None and infer_schema:
-            _args_schema = create_schema_from_function(f"{name}Schema", func)
+            _args_schema = create_schema_from_function(f"{name}Schema", source_function)
         return cls(
             name=name,
             func=func,
+            coroutine=coroutine,
             args_schema=_args_schema,
             description=description,
             return_direct=return_direct,
@@ -720,10 +743,18 @@ def tool(
     """
 
     def _make_with_name(tool_name: str) -> Callable:
-        def _make_tool(func: Callable) -> BaseTool:
+        def _make_tool(dec_func: Callable) -> BaseTool:
+            if inspect.iscoroutinefunction(dec_func):
+                coroutine = dec_func
+                func = None
+            else:
+                coroutine = None
+                func = dec_func
+
             if infer_schema or args_schema is not None:
                 return StructuredTool.from_function(
                     func,
+                    coroutine,
                     name=tool_name,
                     return_direct=return_direct,
                     args_schema=args_schema,
@@ -731,12 +762,17 @@ def tool(
                 )
             # If someone doesn't want a schema applied, we must treat it as
             # a simple string->string function
-            assert func.__doc__ is not None, "Function must have a docstring"
+            if func.__doc__ is None:
+                raise ValueError(
+                    "Function must have a docstring if "
+                    "description not provided and infer_schema is False."
+                )
             return Tool(
                 name=tool_name,
                 func=func,
                 description=f"{tool_name} tool",
                 return_direct=return_direct,
+                coroutine=coroutine,
             )
 
         return _make_tool
diff --git a/libs/langchain/tests/unit_tests/tools/test_base.py b/libs/langchain/tests/unit_tests/tools/test_base.py
index a66953a0669..9c5fdf39e10 100644
--- a/libs/langchain/tests/unit_tests/tools/test_base.py
+++ b/libs/langchain/tests/unit_tests/tools/test_base.py
@@ -546,7 +546,7 @@ def test_tool_with_kwargs() -> None:
 def test_missing_docstring() -> None:
     """Test error is raised when docstring is missing."""
     # expect to throw a value error if there's no docstring
-    with pytest.raises(AssertionError, match="Function must have a docstring"):
+    with pytest.raises(ValueError, match="Function must have a docstring"):
 
         @tool
         def search_api(query: str) -> str: