Implementation:Openai Openai python Response Custom Tool Call Input Delta

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

Overview

Concrete streaming event type representing a partial update to the input of a custom tool call, provided by the openai-python SDK.

Description

ResponseCustomToolCallInputDeltaEvent is a Pydantic model representing a streaming delta event for custom tool call input. As the model generates arguments for a custom tool call, this event delivers incremental delta string chunks. It also includes an item_id linking to the associated API item, an output_index for the output position, a sequence_number for ordering, and a fixed type of "response.custom_tool_call_input.delta". This type is auto-generated from the OpenAI OpenAPI specification by Stainless.

Usage

Import ResponseCustomToolCallInputDeltaEvent when processing streaming events and you need to incrementally assemble the input arguments for a custom tool call as they arrive.

Code Reference

Source Location

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

Signature

class ResponseCustomToolCallInputDeltaEvent(BaseModel):
    """Event representing a delta (partial update) to the input of a custom tool call."""

    delta: str
    item_id: str
    output_index: int
    sequence_number: int
    type: Literal["response.custom_tool_call_input.delta"]

Import

from openai.types.responses import ResponseCustomToolCallInputDeltaEvent

I/O Contract

Fields

Name	Type	Required	Description
delta	str	Yes	The incremental input data (delta) for the custom tool call.
item_id	str	Yes	Unique identifier for the API item associated with this event.
output_index	int	Yes	The index of the output this delta applies to.
sequence_number	int	Yes	The sequence number of this event.
type	Literal["response.custom_tool_call_input.delta"]	Yes	The event type identifier.

Usage Examples

from openai.types.responses import ResponseCustomToolCallInputDeltaEvent

# Accumulate custom tool call input from streaming deltas
input_buffer = ""
for event in stream:
    if isinstance(event, ResponseCustomToolCallInputDeltaEvent):
        input_buffer += event.delta
        print(f"Delta received for item {event.item_id}: {event.delta}")

print(f"Complete input: {input_buffer}")

Related Pages

• Environment:Openai_Openai_python_Python_3_9_Plus