# TraconToolApprovalPolicyExtensions

> 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/api/tracon.tracontoolapprovalpolicyextensions/
> Summary: TraconToolApprovalPolicyExtensions: Chain extension that registers a code-defined approval policy for a tool.

<div class="api-provenance">Namespace Tracon · Assembly <code>Tracon.Core.dll</code></div>

Chain extension that registers a code-defined approval policy for a tool.

```csharp
public static class TraconToolApprovalPolicyExtensions
```

<dl class="api-relations"><dt>Inheritance</dt><dd><a href="https://learn.microsoft.com/dotnet/api/system.object">object</a> ← <a href="/api/tracon.tracontoolapprovalpolicyextensions/">TraconToolApprovalPolicyExtensions</a></dd><dt>Inherited Members</dt><dd><a href="https://learn.microsoft.com/dotnet/api/system.object.gettype">object.GetType()</a>, <a href="https://learn.microsoft.com/dotnet/api/system.object.memberwiseclone">object.MemberwiseClone()</a>, <a href="https://learn.microsoft.com/dotnet/api/system.object.tostring">object.ToString()</a>, <a href="https://learn.microsoft.com/dotnet/api/system.object.equals#system-object-equals(system-object)">object.Equals(object?)</a>, <a href="https://learn.microsoft.com/dotnet/api/system.object.equals#system-object-equals(system-object-system-object)">object.Equals(object?, object?)</a>, <a href="https://learn.microsoft.com/dotnet/api/system.object.referenceequals">object.ReferenceEquals(object?, object?)</a>, <a href="https://learn.microsoft.com/dotnet/api/system.object.gethashcode">object.GetHashCode()</a></dd></dl>

## Remarks

This is an extension method, not a member of [ITraconBuilder](/api/tracon.itraconbuilder/):
adding a member to the interface is a breaking change after release; adding
an extension method is not.

## Methods

### <a id="Tracon_TraconToolApprovalPolicyExtensions_AddToolApprovalPolicy_Tracon_ITraconBuilder_System_String_System_Func_Tracon_ToolApprovalContext_Tracon_ToolApprovalPolicyDecision__"></a> AddToolApprovalPolicy\(ITraconBuilder, string, Func<ToolApprovalContext, ToolApprovalPolicyDecision\>\)

Registers a code-defined approval policy for a tool.

```csharp
public static ITraconBuilder AddToolApprovalPolicy(this ITraconBuilder builder, string toolName, Func<ToolApprovalContext, ToolApprovalPolicyDecision> policy)
```

#### Parameters

`builder` [ITraconBuilder](/api/tracon.itraconbuilder/)

The configuration chain.

`toolName` [string](https://learn.microsoft.com/dotnet/api/system.string)

The tool the policy judges.

`policy` [Func](https://learn.microsoft.com/dotnet/api/system.func\-2)<[ToolApprovalContext](/api/tracon.toolapprovalcontext/), [ToolApprovalPolicyDecision](/api/tracon.toolapprovalpolicydecision/)\>

The policy delegate. Runs at every call to `toolName`, before the
data rules ([ToolApprovalRule](/api/tracon.toolapprovalrule/)). [ToolApprovalPolicyDecision.Required](/api/tracon.toolapprovalpolicydecision/)
and [ToolApprovalPolicyDecision.NotRequired](/api/tracon.toolapprovalpolicydecision/) override the data rules;
[ToolApprovalPolicyDecision.Undecided](/api/tracon.toolapprovalpolicydecision/) defers to them. An exception is treated
as [ToolApprovalPolicyDecision.Required](/api/tracon.toolapprovalpolicydecision/) and logged — a broken policy does not
silently release a tool from approval.

#### Returns

 [ITraconBuilder](/api/tracon.itraconbuilder/)

The chain, for further configuration.

#### Remarks

The policy's dependencies must be captured at REGISTRATION time (the
delegate's closure), not resolved from a service provider inside the
delegate — the service provider a tool call sees is empty.

```csharp
builder.AddTracon()
       .AddToolApprovalPolicy("refund_order", context =>
           context.GetNumber("amount") is { } amount && amount <= 100
               ? ToolApprovalPolicyDecision.NotRequired
               : ToolApprovalPolicyDecision.Required);
```

#### Exceptions

 [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception)

`builder` or `policy` is [null](https://learn.microsoft.com/dotnet/csharp/language-reference/keywords/null).

 [ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception)

`toolName` is empty or whitespace.