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Setup

npm i ai @google/genai @nangohq/node
This example uses the Node SDK, a lightweight wrapper over Nango’s REST API. The same flow works in any language by using the API reference.
Requirements:
  • A Nango account with a Hubspot integration configured and the whoami action enabled.
  • A Google Gemini account.

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Usage

Example of a basic tool that calls an external API (Hubspot): 
import { GoogleGenAI, FunctionCallingConfigMode, Type } from "@google/genai";
import { Nango } from "@nangohq/node";

export async function runGoogleAgent() {
  if (!process.env.GOOGLE_API_KEY) {
    console.log("Missing environment variable: GOOGLE_API_KEY.");
  }

  const ai = new GoogleGenAI({ apiKey: process.env.GOOGLE_API_KEY! });
  const nango = new Nango({ secretKey: process.env.NANGO_SECRET_KEY! });

  const userId = "user1", integrationId = "hubspot";

  // Step 1: Ensure the user is authorized
  console.log("🔒 Checking API authorization...");
  let connectionId = (await nango.listConnections({ integrationId, userId })).connections[0]?.connection_id;

  // Step 2: If the user is not authorized, redirect to the auth flow.
  if (!connectionId) {
    const session = await nango.createConnectSession({
      allowed_integrations: [integrationId],
      end_user: { id: userId },
    });

    console.log(`Please authorize the app by visiting this URL: ${session.data.connect_link}`);

    const connection = await nango.waitForConnection(integrationId, userId);
    connectionId = connection!.connection_id;
  }

  // Step 3: Send a prompt to your model with tool definitions
  console.log("🤖 Agent running...");
  const response = await ai.models.generateContent({
    model: "gemini-2.5-flash",
    contents: "Using the who_am_i tool, provide the current user info.",
    config: {
      toolConfig: {
        functionCallingConfig: {
          mode: FunctionCallingConfigMode.ANY,
          allowedFunctionNames: ["who_am_i"],
        },
      },
      tools: [
        {
          functionDeclarations: [
            {
              name: "who_am_i",
              description: "Get the current user info.",
              parameters: {
                type: Type.OBJECT,
                properties: {},
                required: [],
              },
            },
          ],
        },
      ],
    },
  });

  const functionCall = response.functionCalls?.[0];

  if (functionCall?.name === "who_am_i") {
    // Step 4: Execute the requested tool with Nango.
    const userInfo = await nango.triggerAction(integrationId, connectionId, "whoami");
    console.log("✅ Agent retrieved your Hubspot user info:", userInfo);
  } else {
    console.log(response.text);
  }
}
You can let agents or models introspect available tools and their specifications by calling this endpoint. Your model can then automatically decide which tool to call.