---
title: "ReasoningDetailServerToolCall"
---

Record of an OpenRouter server-tool invocation (e.g. openrouter:fusion), carried in reasoning_details so a prior tool call can be rehydrated into a later turn of the same conversation.


## Fields

| Field                                                                                              | Type                                                                                               | Required                                                                                           | Description                                                                                        | Example                                                                                            |
| -------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------- |
| `arguments`                                                                                        | *str*                                                                                              | :heavy_check_mark:                                                                                 | N/A                                                                                                |                                                                                                    |
| `format_`                                                                                          | [OptionalNullable[components.ReasoningFormat]](../components/reasoningformat.mdx)                   | :heavy_minus_sign:                                                                                 | N/A                                                                                                | unknown                                                                                            |
| `id`                                                                                               | *OptionalNullable[str]*                                                                            | :heavy_minus_sign:                                                                                 | N/A                                                                                                |                                                                                                    |
| `index`                                                                                            | *Optional[int]*                                                                                    | :heavy_minus_sign:                                                                                 | N/A                                                                                                |                                                                                                    |
| `result`                                                                                           | *str*                                                                                              | :heavy_check_mark:                                                                                 | N/A                                                                                                |                                                                                                    |
| `tool_call_id`                                                                                     | *OptionalNullable[str]*                                                                            | :heavy_minus_sign:                                                                                 | N/A                                                                                                |                                                                                                    |
| `tool_name`                                                                                        | *str*                                                                                              | :heavy_check_mark:                                                                                 | N/A                                                                                                |                                                                                                    |
| `type`                                                                                             | [components.ReasoningDetailServerToolCallType](../components/reasoningdetailservertoolcalltype.mdx) | :heavy_check_mark:                                                                                 | N/A                                                                                                |                                                                                                    |