providerToolSearchMiddleware

import { createAgent, providerToolSearchMiddleware } from "langchain";
import { ChatAnthropic } from "@langchain/anthropic";

const agent = createAgent({
  model: new ChatAnthropic({ model: "claude-sonnet-4-5" }),
  tools: [getWeather, ...nicheTools],
  middleware: [
    // Defer the niche tools behind the provider's tool search; the model
    // discovers them on demand instead of receiving every schema up front.
    providerToolSearchMiddleware({ searchableTools: nicheTools }),
  ],
});

import { tool } from "@langchain/core/tools";
import { createAgent, providerToolSearchMiddleware } from "langchain";
import { ChatAnthropic } from "@langchain/anthropic";

// A tool marked `defer_loading` at construction is deferred on its own —
// no need to list it in `searchableTools`; the middleware honors the flag.
const sendEmail = tool(sendEmailFn, {
  name: "send_email",
  description: "Send an email",
  schema: sendEmailSchema,
  extras: { defer_loading: true },
});

const agent = createAgent({
  model: new ChatAnthropic({ model: "claude-sonnet-4-5" }),
  tools: [getWeather, sendEmail],
  middleware: [providerToolSearchMiddleware()],
});