On Type Safety In LangChain TS

snippet-1.ts

import { z } from "zod";
import { StructuredTool } from "langchain/tools";

const clickSchema = z.object({
  selector: z.string().describe("The query seletor to click on."),
});

const ClickSchema = z.infer<typeof clickSchema>;

class ClickTool extends StructuredTool<typeof clickSchema> {
  schema = clickSchema;
  name = "click";
  description =
    "left click on an element on a web page represented by a query selector";

  protected _call(arg: ClickSchema): Promise<string> {
    // We need to know that arg.selector is a thing here
    return this.click(arg.selector);
  }

  private click(selector: string): Promise<string> {
    // Add actual implementation of clicking
    return Promise.resolve(`Clicked on ${selector}`);
  }
}