injectRegisterViewTool

injectRegisterViewTool<TInput extends ZodRawShapeCompat>(
  config: ViewToolConfig<TInput>,
  handler: ViewToolHandler<TInput>,
): RegisterViewToolHandle

A server tool runs on your server. A view tool runs in the view, in the browser, with your component state in scope. Use it when the model must act on what is already on screen.

import { injectRegisterViewTool } from "ng-mcp-ui/web";
import { z } from "zod";

export class ChessWidget {
  private readonly board = signal(initialBoard());

  private readonly handle = injectRegisterViewTool(
    {
      name: "chess_make_move",
      description: "Move a piece on the board that is on screen.",
      inputSchema: { from: z.string(), to: z.string() },
    },
    ({ from, to }) => {
      this.board.update((b) => applyMove(b, from, to));
      return { content: [{ type: "text", text: `Moved ${from} to ${to}.` }] };
    },
  );
}

Config

Field	Type	Purpose
name	string	The identifier of the tool.
title	string, optional	A label for people.
description	string, optional	Tells the model when to call it.
inputSchema	Zod shape, optional	The arguments. The handler gets them typed.
annotations	ToolAnnotations, optional	The standard MCP annotations.

Give the name a namespace, for example chess_make_move. A view tool and a server tool share one name space, therefore a plain name can collide.

Handler

The handler receives typed, validated arguments. It returns a CallToolResult: content blocks, with optional structuredContent, isError and _meta.

The handler runs in the browser. Therefore it can read and write your signals directly, and the change appears immediately.

Returns

RegisterViewToolHandle has one member.

Member	Purpose
unregister()	Removes the tool.

The registration is also removed when the injection context is destroyed. Call unregister() yourself only to remove the tool while the view stays up.

Host support

Host	Behavior
Apps SDK	No operation. The call writes a warning and returns an empty disposer.
MCP Apps	Supported.

The empty disposer means your cleanup code stays correct on the two hosts. A view that needs this feature must still work on an Apps SDK host, therefore keep an equivalent server tool, or a control that the user can operate.

Related

• injectCallTool
• Host support