diff --git a/haystack/tools/from_function.py b/haystack/tools/from_function.py
index 67fd476207..c185fab47c 100644
--- a/haystack/tools/from_function.py
+++ b/haystack/tools/from_function.py
@@ -3,6 +3,8 @@
# SPDX-License-Identifier: Apache-2.0
import inspect
+import re
+import textwrap
from typing import Any, Callable, Dict, Optional
from pydantic import create_model
@@ -10,6 +12,9 @@
from haystack.tools.errors import SchemaGenerationError
from haystack.tools.tool import Tool
+# Define constants for ReST directives
+REST_DIRECTIVES = r"param|return|returns|raise|raises"
+
def create_tool_from_function(
function: Callable, name: Optional[str] = None, description: Optional[str] = None
@@ -72,7 +77,53 @@ def get_weather(
If there is an error generating the JSON schema for the Tool.
"""
- tool_description = description if description is not None else (function.__doc__ or "")
+ tool_description = ""
+ param_descriptions_from_rest: Dict[str, str] = {}
+ return_description = ""
+ raises_descriptions = []
+
+ if description is not None:
+ tool_description = description
+ else:
+ # Process docstring if available
+ if function.__doc__:
+ docstring = textwrap.dedent(function.__doc__).strip()
+
+ # Check if this is a ReST-style docstring
+ if re.search(rf":({REST_DIRECTIVES})\s+", docstring):
+ # Extract main description (everything before first directive)
+ main_parts = re.split(rf":({REST_DIRECTIVES})\s+", docstring, 1)
+ tool_description = main_parts[0].strip()
+
+ # Parse parameter descriptions (handling both :param name: and :param type name: formats)
+ param_pattern = re.compile(rf":param\s+(\w+)\s*:(.*?)(?=:(?:{REST_DIRECTIVES})|$)", re.DOTALL)
+ param_descriptions_from_rest = {name: desc.strip() for name, desc in param_pattern.findall(docstring)}
+
+ # Parse return descriptions
+ return_pattern = re.compile(rf":return:\s*(.*?)(?=:(?:{REST_DIRECTIVES})|$)", re.DOTALL)
+ return_matches = return_pattern.findall(docstring)
+ if return_matches:
+ return_description = return_matches[0].strip()
+
+ # Parse raises descriptions
+ raises_pattern = re.compile(
+ rf":raises?\s+(\w+(?:,\s*\w+)*)\s*:\s*(.*?)(?=:(?:{REST_DIRECTIVES})|$)", re.DOTALL
+ )
+ for exc_types, desc in raises_pattern.findall(docstring):
+ for exc_type in re.split(r",\s*", exc_types):
+ raises_descriptions.append(f"{exc_type}: {desc.strip()}")
+ else:
+ # Not a ReST-style docstring, use the whole thing
+ tool_description = docstring.strip()
+
+ # Build a comprehensive description including return values and exceptions
+ full_description = tool_description
+
+ if return_description:
+ full_description += f"\n\nReturns: {return_description}"
+
+ if raises_descriptions:
+ full_description += "\n\nRaises:\n" + "\n".join(f"- {r}" for r in raises_descriptions)
signature = inspect.signature(function)
@@ -89,8 +140,12 @@ def get_weather(
default = param.default if param.default is not param.empty else ...
fields[param_name] = (param.annotation, default)
+ # Priority 1: Get descriptions from Annotated type hints
if hasattr(param.annotation, "__metadata__"):
descriptions[param_name] = param.annotation.__metadata__[0]
+ # Priority 2: Get descriptions from ReST docstring
+ elif param_name in param_descriptions_from_rest:
+ descriptions[param_name] = param_descriptions_from_rest[param_name]
# create Pydantic model and generate JSON schema
try:
@@ -109,7 +164,7 @@ def get_weather(
if param_name in schema["properties"]:
schema["properties"][param_name]["description"] = param_description
- return Tool(name=name or function.__name__, description=tool_description, parameters=schema, function=function)
+ return Tool(name=name or function.__name__, description=full_description, parameters=schema, function=function)
def tool(function: Callable) -> Tool:
diff --git a/releasenotes/notes/tool-from-function-with-rest-docstring-fa2728ec718db524.yaml b/releasenotes/notes/tool-from-function-with-rest-docstring-fa2728ec718db524.yaml
new file mode 100644
index 0000000000..f9d302d386
--- /dev/null
+++ b/releasenotes/notes/tool-from-function-with-rest-docstring-fa2728ec718db524.yaml
@@ -0,0 +1,6 @@
+---
+features:
+ - |
+ Supports ReST-style docstrings for functions when generating a tool from a function.
+ The ReST-style docstring will be automatically parsed to infer the tool's description and
+ argument descriptions.
diff --git a/test/tools/test_from_function.py b/test/tools/test_from_function.py
index 5834b737d4..da75bbe2df 100644
--- a/test/tools/test_from_function.py
+++ b/test/tools/test_from_function.py
@@ -10,6 +10,19 @@ def function_with_docstring(city: str) -> str:
return f"Weather report for {city}: 20°C, sunny"
+def function_with_rest_docstring(city: str) -> str:
+ """
+ Get weather report for a city.
+
+ :param city: The city for which to get the weather.
+ :return: The weather report for the city.
+ :raises ValueError: If the city is not found.
+ """
+ if city == "":
+ raise ValueError("City not found.")
+ return f"Weather report for {city}: 20°C, sunny"
+
+
def test_from_function_description_from_docstring():
tool = create_tool_from_function(function=function_with_docstring)
@@ -19,6 +32,23 @@ def test_from_function_description_from_docstring():
assert tool.function == function_with_docstring
+def test_from_function_description_from_rest_docstring():
+ tool = create_tool_from_function(function=function_with_rest_docstring)
+
+ assert tool.name == "function_with_rest_docstring"
+ assert tool.description == (
+ "Get weather report for a city.\n\n"
+ "Returns: The weather report for the city.\n\n"
+ "Raises:\n- ValueError: If the city is not found."
+ )
+ assert tool.parameters == {
+ "type": "object",
+ "properties": {"city": {"type": "string", "description": "The city for which to get the weather."}},
+ "required": ["city"],
+ }
+ assert tool.function == function_with_rest_docstring
+
+
def test_from_function_with_empty_description():
tool = create_tool_from_function(function=function_with_docstring, description="")