---
title: "Create agent session input events"
method: POST
path: "/agents/sessions/{session_id}/events"
tags: ["Agents"]
---

# Create agent session input events

`POST /agents/sessions/{session_id}/events`

Submits message, cancellation, or tool-result events to a managed agent session. See [session events](https://developers.openai.com/api/docs/guides/agents-api/sessions/events).

## Path parameters

- `session_id` string, required

## Headers

- `Idempotency-Key` string

## Request body

- CreateSessionEventsParams — Input events submitted to an existing session.
  - `events` SessionInputParam[], required — The input events to submit to the session.
    - union — Input submitted to an existing session.
      - object — Adds one or more user messages and starts a turn.
        - `type` 'agent.session.input.message', required — The type of the object. Always `agent.session.input.message`.
        - `input` InputMessageParam[], required — The user messages to add to the session.
          - `type` 'message' — The type of the input item. Always `message`.
          - `role` 'user', required — The role of the message author. Always `user`.
          - `content` InputContentParam[], required — The content of the message.
            - union — Content included in an input message.
              - …
      - object — Cancels the session's active turn.
        - `type` 'agent.session.input.cancel', required — The type of the object. Always `agent.session.input.cancel`.
      - object — Submits the result of a function call.
        - `type` 'agent.session.input.tool_result', required — The type of the object. Always `agent.session.input.tool_result`.
        - `turn_id` string, required — The ID of the turn that requested the function call.
        - `call_id` string, required — The ID of the function call.
        - `success` boolean, required — Whether the function call succeeded.
        - `output` union — A function result represented as text or supported model-input content.
          - string
          - InputContentParam[]
            - union — Content included in an input message.
              - …
        - `error` string, nullable — The error message when the call failed.

## Response `202`

The events were accepted.

## Other responses

- `400` — The request was invalid.
- `401` — Authentication or project context was missing.
- `403` — The API key lacks the required permission.
- `404` — The requested session or event was not found.
- `409` — The request conflicted with the current session state.
- `500` — An internal error occurred.
- `503` — The service is temporarily unavailable.

## Changes

- **2026-09-10** `f2dae1a9aced` — 1 info
  - endpoint added

[Change history](https://skmtc.dev/openai/apis/openapi/changes/agents/sessions/:session_id/events/post.md)

---

[API](https://skmtc.dev/openai/apis/openapi.md) · [All operations](https://skmtc.dev/openai/apis/openapi/llms.txt) · [OpenAPI document](https://skmtc.dev/openai/apis/openapi/revisions/c8bd56db4095?raw)