# TraconClientToolExtensions
> 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.traconclienttoolextensions/
> Summary: TraconClientToolExtensions: Registers a client-side tool: its declaration (name, description, JSON schema) lives in code, like every other tool (the code-only tools rule), but its body runs.
Namespace Tracon ยท Assembly Tracon.Core.dll
Registers a client-side tool: its declaration (name, description, JSON
schema) lives in code, like every other tool (the code-only tools rule), but its
body runs on the caller instead of on the server.
```csharp
public static class TraconClientToolExtensions
```
- Inheritance
- object โ TraconClientToolExtensions
- Inherited Members
- object.GetType(), object.MemberwiseClone(), object.ToString(), object.Equals(object?), object.Equals(object?, object?), object.ReferenceEquals(object?, object?), object.GetHashCode()
## Methods
### AddClientTool\(ITraconBuilder, string, string, JsonElement\)
Registers a tool whose body the server never runs.
```csharp
public static ITraconBuilder AddClientTool(this ITraconBuilder builder, string name, string description, JsonElement jsonSchema)
```
#### Parameters
`builder` [ITraconBuilder](/api/tracon.itraconbuilder/)
The Tracon configuration chain.
`name` [string](https://learn.microsoft.com/dotnet/api/system.string)
The tool name. Must be unique among all registered tools.
`description` [string](https://learn.microsoft.com/dotnet/api/system.string)
The description that lets the model understand when to call the tool.
`jsonSchema` [JsonElement](https://learn.microsoft.com/dotnet/api/system.text.json.jsonelement)
The arguments' JSON schema.
#### Returns
[ITraconBuilder](/api/tracon.itraconbuilder/)
The chain, for further configuration.
#### Remarks
The model can call the tool, but the server produces a
`FunctionCallContent` and returns it to the caller instead of
running anything โ Microsoft Agent Framework's
`FunctionInvokingChatClient` only invokes an `AIFunction`;
a declaration-only `AIFunctionDeclaration` is not one. The
caller (typically a browser) runs the tool itself and sends the
result back via `AgentRunRequest.ToolResults`
(`Tracon.AspNetCore`) to let the turn continue.
A client-side tool cannot require approval โ there is no server-side
body to defer. [Tracon.ToolRegistry](/api/tracon/) rejects that combination at
startup if attempted through a direct
[TraconToolRegistration](/api/tracon.tracontoolregistration/) registration.
```csharp
var schema = JsonSerializer.Deserialize(
"""{"type":"object","properties":{"path":{"type":"string"}}}""");
builder.AddTracon()
.AddClientTool("open_page", "Opens a page in the user's browser.", schema);
```
#### Exceptions
[ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception)
`builder` is [null](https://learn.microsoft.com/dotnet/csharp/language-reference/keywords/null).
[ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception)
`name` or `description` is empty.