Implementation:Openai Openai python Custom Tool Param

Knowledge Sources	Openai_Openai_python OpenAI API Reference
Domains	API_Types, Python
Last Updated	2026-02-15 00:00 GMT

Overview

Concrete type for parameterizing a custom tool in a request provided by the openai-python SDK.

Description

CustomToolParam is a TypedDict that defines the parameter structure for specifying a custom tool in a Responses API request. It requires a name field (string identifying the tool in tool calls) and a type field fixed to "custom". Optional fields include description (providing more context about the tool) and format of type CustomToolInputFormat (specifying the input format, defaulting to unconstrained text).

Usage

Import this type when constructing a tool list for a response request that includes custom tools. This is the request parameter counterpart to the CustomTool response model.

Code Reference

Source Location

• Repository: openai-python
• File: src/openai/types/responses/custom_tool_param.py

Signature

class CustomToolParam(TypedDict, total=False):
    """A custom tool that processes input using a specified format."""
    name: Required[str]
    type: Required[Literal["custom"]]
    description: str
    format: CustomToolInputFormat

Import

from openai.types.responses import CustomToolParam

I/O Contract

Fields

Name	Type	Required	Description
name	str	Yes	The name of the custom tool, used to identify it in tool calls.
type	Literal["custom"]	Yes	The type of the custom tool. Always "custom".
description	str	No	Optional description of the custom tool, used to provide more context.
format	CustomToolInputFormat	No	The input format for the custom tool. Default is unconstrained text.

Usage Examples

from openai.types.responses import CustomToolParam

tool: CustomToolParam = {
    "type": "custom",
    "name": "weather_lookup",
    "description": "Looks up current weather for a city",
}

response = client.responses.create(
    model="gpt-4o",
    tools=[tool],
    input="What is the weather in San Francisco?",
)

Related Pages

• Environment:Openai_Openai_python_Python_3_9_Plus