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Overview

The Tool class allows you to wrap Python functions—synchronous or asynchronous—with input validation, rich metadata, and compatibility with LLM agent frameworks such as LangChain. It enables:
  • Pydantic-based input validation
  • Safe execution of async and sync functions
  • Metadata generation for prompt or UI integration
  • Seamless conversion to LangChain StructuredTool

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Basic Usage

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Simple Sync Function

from chainless import Tool

def greet(name: str):
    return f"Hello, {name}!"

tool = Tool("Greeter", "Greets a person by name", greet)
tool.execute({"name": "Alice"})
# Output: "Hello, Alice!"

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With Async Function

import asyncio

async def async_greet(name: str):
    return f"Hi (async), {name}!"

tool = Tool("AsyncGreeter", "Asynchronous greeting", async_greet)
await tool.execute({"name": "Bob"})

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Input Validation with Pydantic

You can provide a schema to ensure input data is validated before execution. 
from pydantic import BaseModel

class GreetSchema(BaseModel):
    name: str

tool = Tool("Greeter", "Greets a person", greet, input_schema=GreetSchema)

# Valid
tool.execute({"name": "Alice"})

# Invalid (raises ToolInputValidationError)
tool.execute({"name": 123})

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Attributes

NameTypeDescription
namestrUnique identifier for the tool
descriptionstrUsed in UIs and LLM prompt construction
funcCallableThe actual function (sync or async) to execute
input_schemaOptional[BaseModel]Pydantic schema for validating and describing tool inputs
raise_on_errorbool (default=True)If False, will suppress exceptions and log errors

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Metadata via describe()

tool.describe()

# Output:
{
  "name": "Greeter",
  "description": "Greets a person",
  "parameters": {
    "name": {
      "type": "string",
      "description": "No description provided."
    }
  }
}

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LangChain Integration

structured_tool = tool.convert_tool_to_langchain()

# Pass to a LangChain agent
agent = initialize_agent([structured_tool], llm=llm, ...)

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Error Handling

If validation fails, a ToolInputValidationError will be raised with detailed information: 
try:
    tool.execute({"name": 42})
except ToolInputValidationError as err:
    print(err)

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Real-World Example

from chainless import Tool, Agent

def get_weather(city: str):
    return f"{city} is sunny today."

weather_tool = Tool("WeatherTool", "Provides current weather", get_weather)

agent = Agent(
  name="WeatherAgent",
  llm=llm,
  tools=[weather_tool],
  system_prompt="Only respond using weather tool."
)

response = agent.start("What's the weather in Istanbul?")
print(response)

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Best Practices

  • Keep tool functions pure and stateless
  • Always define an input schema for clarity and safety
  • Use describe() to integrate with UIs or LLM-based planning systems
  • Avoid side effects inside tool logic (e.g. file writes or database mutations)

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Interface Summary

interface Tool {
  name: string;
  description: string;
  execute(input: Record<string, any>): Promise<any>;
  describe(): {
    name: string;
    description: string;
    parameters: Record<string, any>;
  };
}
Tools are the building blocks for agent autonomy. Define them clearly, validate inputs properly, and structure them for reusability. They integrate seamlessly into the Chainless Agent and TaskFlow system for powerful orchestration.