# ToolUsage

> Tracon documentation. Tracon is a .NET package family that adds a control
> plane on Microsoft Agent Framework, published as NuGet packages that run
> inside your own ASP.NET Core application.
>
> Page: https://tracon.dev/http-api/schemas/toolusage/
> Summary: OpenAPI request or response schema for ToolUsage, including required fields, defaults, constraints, and linked nested types.

[← All HTTP schemas](/http-api/schemas/)

A tool's usage summary. Shown by the UI's Tools screen.

**Shape:** `object`

| Property | Required | Type | Description | Rules |
|---|---|---|---|---|
| `toolName` | yes | `string` | The tool name. | — |
| `totalCalls` | yes | `integer (int64)` | The total number of calls. | pattern `^-?(?:0\\|[1-9]\d*)$` |
| `failedCalls` | yes | `integer (int64)` | The number of calls that errored. | pattern `^-?(?:0\\|[1-9]\d*)$` |
| `averageDurationMs` | no | `number (double)` | The average duration (milliseconds). `null` if no call carries a duration. | pattern `^-?(?:0\\|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?$` |
| `lastCalledAt` | no | `string (date-time)` | The moment it was last called (UTC). | — |
| `errorRate` | no | `number (double)` | The error rate among settled calls (0–1). `null` if there is no call. | pattern `^-?(?:0\\|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?$` |