Method executeToolHandler

packages/core/src/core/run-handler.ts:489–595

* Shared handler execution logic used by executeSpecificTool, executeWildcardTool, and runTool. * Handles arg parsing, subscriber notifications, handler invocation, result stringification, * and error handling.

({
    tool,
    toolCall,
    agent,
    agentId,
    handlerArgs,
    toolType,
    messageId,
  }: {
    tool: FrontendTool<any>;
    toolCall: { id: string; function: { name: string; arguments: string } };
    agent: AbstractAgent;
    agentId: string;
    handlerArgs: unknown;
    toolType: string;
    messageId?: string;
  })

   * and error handling.
   */
  private async executeToolHandler({
    tool,
    toolCall,
    agent,
    agentId,
    handlerArgs,
    toolType,
    messageId,
  }: {
    tool: FrontendTool<any>;
    toolCall: { id: string; function: { name: string; arguments: string } };
    agent: AbstractAgent;
    agentId: string;
    handlerArgs: unknown;
    toolType: string;
    messageId?: string;
  }): Promise<ExecuteToolHandlerResult> {
    let toolCallResult = "";
    let errorMessage: string | undefined;
    let isArgumentError = false;

    let parsedArgs: unknown;
    try {
      parsedArgs = parseToolArguments(handlerArgs, toolCall.function.name);
    } catch (error) {
      const parseError =
        error instanceof Error ? error : new Error(String(error));
      errorMessage = parseError.message;
      isArgumentError = true;
      await this._internal.emitError({
        error: parseError,
        code: CopilotKitCoreErrorCode.TOOL_ARGUMENT_PARSE_FAILED,
        context: {
          agentId,
          toolCallId: toolCall.id,
          toolName: toolCall.function.name,
          rawArguments: handlerArgs,
          toolType,
          ...(messageId ? { messageId } : {}),
        },
      });
    }

    await this._internal.notifySubscribers(
      (subscriber) =>
        subscriber.onToolExecutionStart?.({
          copilotkit: this.core,
          toolCallId: toolCall.id,
          agentId,
          toolName: toolCall.function.name,
          args: parsedArgs,
        }),
      "Subscriber onToolExecutionStart error:",
    );

    if (!errorMessage) {
      try {
        const result = await tool.handler!(parsedArgs as any, {