---
title: "CustomToolCallItem"
---

A call to a custom (freeform-grammar) tool created by the model — distinct from `function_call`. Used for tools like Codex CLI's `apply_patch` whose payload is opaque text rather than JSON arguments.


## Fields

| Field                                                                                           | Type                                                                                            | Required                                                                                        | Description                                                                                     |
| ----------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------- |
| `call_id`                                                                                       | *str*                                                                                           | :heavy_check_mark:                                                                              | N/A                                                                                             |
| `id`                                                                                            | *Optional[str]*                                                                                 | :heavy_minus_sign:                                                                              | N/A                                                                                             |
| `input`                                                                                         | *str*                                                                                           | :heavy_check_mark:                                                                              | N/A                                                                                             |
| `name`                                                                                          | *str*                                                                                           | :heavy_check_mark:                                                                              | N/A                                                                                             |
| `namespace`                                                                                     | *Optional[str]*                                                                                 | :heavy_minus_sign:                                                                              | Namespace qualifier for tools registered as part of a namespace tool group (e.g. an MCP server) |
| `type`                                                                                          | [components.CustomToolCallItemType](../components/customtoolcallitemtype.mdx)                    | :heavy_check_mark:                                                                              | N/A                                                                                             |