# TraconExternalCallException

> 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.traconexternalcallexception/
> Summary: TraconExternalCallException: Thrown when an external caller (over MCP or A2A) asked to invoke an agent from the catalog and the call was refused because it crosses a boundary.

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

Thrown when an external caller (over MCP or A2A) asked to invoke an agent from
the catalog and the call was refused because it crosses a boundary.

```csharp
public sealed class TraconExternalCallException : TraconException, ISerializable
```

<dl class="api-relations"><dt>Inheritance</dt><dd><a href="https://learn.microsoft.com/dotnet/api/system.object">object</a> ← <a href="https://learn.microsoft.com/dotnet/api/system.exception">Exception</a> ← <a href="/api/tracon.traconexception/">TraconException</a> ← <a href="/api/tracon.traconexternalcallexception/">TraconExternalCallException</a></dd><dt>Implements</dt><dd><a href="https://learn.microsoft.com/dotnet/api/system.runtime.serialization.iserializable">ISerializable</a></dd><dt>Inherited Members</dt><dd><a href="/api/tracon.traconexception/#Tracon_TraconException_ErrorType">TraconException.ErrorType</a>, <a href="https://learn.microsoft.com/dotnet/api/system.exception.getbaseexception">Exception.GetBaseException()</a>, <a href="https://learn.microsoft.com/dotnet/api/system.exception.tostring">Exception.ToString()</a>, <a href="https://learn.microsoft.com/dotnet/api/system.exception.gettype">Exception.GetType()</a>, <a href="https://learn.microsoft.com/dotnet/api/system.exception.targetsite">Exception.TargetSite</a>, <a href="https://learn.microsoft.com/dotnet/api/system.exception.message">Exception.Message</a>, <a href="https://learn.microsoft.com/dotnet/api/system.exception.data">Exception.Data</a>, <a href="https://learn.microsoft.com/dotnet/api/system.exception.innerexception">Exception.InnerException</a>, <a href="https://learn.microsoft.com/dotnet/api/system.exception.helplink">Exception.HelpLink</a>, <a href="https://learn.microsoft.com/dotnet/api/system.exception.source">Exception.Source</a>, <a href="https://learn.microsoft.com/dotnet/api/system.exception.hresult">Exception.HResult</a>, <a href="https://learn.microsoft.com/dotnet/api/system.exception.stacktrace">Exception.StackTrace</a>, <a href="https://learn.microsoft.com/dotnet/api/system.object.gettype">object.GetType()</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

The most common cause is an external caller trying to open an agent that carries
a tool requiring approval. An external caller is not an agent and cannot answer
an approval request — the same rule, applied a second time.

## Constructors

### <a id="Tracon_TraconExternalCallException__ctor"></a> TraconExternalCallException\(\)

Creates a new error.

```csharp
public TraconExternalCallException()
```

### <a id="Tracon_TraconExternalCallException__ctor_System_String_"></a> TraconExternalCallException\(string\)

Creates a new error.

```csharp
public TraconExternalCallException(string message)
```

#### Parameters

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

The error message.

### <a id="Tracon_TraconExternalCallException__ctor_System_String_System_Exception_"></a> TraconExternalCallException\(string, Exception\)

Creates a new error.

```csharp
public TraconExternalCallException(string message, Exception innerException)
```

#### Parameters

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

The error message.

`innerException` [Exception](https://learn.microsoft.com/dotnet/api/system.exception)

The underlying error.

## Fields

### <a id="Tracon_TraconExternalCallException_ExternalCallRejectedErrorType"></a> ExternalCallRejectedErrorType

The stable value written to [TraconException.ErrorType](/api/tracon.traconexception/#Tracon_TraconException_ErrorType).

```csharp
public const string ExternalCallRejectedErrorType = "external_call_rejected"
```

#### Field Value

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

## Properties

### <a id="Tracon_TraconExternalCallException_AgentName"></a> AgentName

Gets the agent the caller asked for.

```csharp
public required string AgentName { get; init; }
```

#### Property Value

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

### <a id="Tracon_TraconExternalCallException_ErrorType"></a> ErrorType

Gets the stable error type name written to the run record.

```csharp
public override string ErrorType { get; }
```

#### Property Value

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

#### Remarks

Defaults to the full name of the exception type, so today's behaviour does
not change. A derived type overrides this member when the record has to be
machine readable — for example [TraconContentFilteredException](/api/tracon.traconcontentfilteredexception/)
writes `content_filtered`. Reports and alert rules can rely on this
stable name instead of an assembly name.

The value is written to `RunError.Type` and **carries no secret**.

### <a id="Tracon_TraconExternalCallException_Protocol"></a> Protocol

Gets the protocol the call arrived on: `mcp` or `a2a`.

```csharp
public required string Protocol { get; init; }
```

#### Property Value

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