Tools

A tool is an HTTPS endpoint of yours that the agent can call mid-conversation, with arguments it collects from the caller. Use tools to look up an order, check availability, book a meeting, open a ticket or update your CRM. The endpoint can be your own server, or a Zapier, Make or n8n webhook. Set them up on the editor’s Tools tab.

Built-in: End call

End call (on by default) lets the agent hang up once it has said goodbye, or when the caller asks to end the call. The call ends after the goodbye has finished playing, and the caller sees Call ended.

Add a custom tool

Click Add tool and fill in:

Field	Description
Function name	What the agent calls it, such as `get_order_status`. Letters, numbers, `_` and `-`, up to 64 characters. Unique per agent, and not `end_call`.
Endpoint (POST)	Your URL. Must start with `https://`.
When to use it	A description the agent reads to decide when to call the tool. Up to 1,000 characters.
Parameters (JSON Schema)	The arguments to collect, as a JSON Schema object (`{ "type": "object", … }`).
Headers (optional)	Sent with every request, one per line as `Name: value`, such as your endpoint’s auth. Up to 10.

An agent can have up to 20 custom tools.

Example

Function name: get_order_status When to use it: Look up an order’s delivery status by its order number. Parameters:

{
  "type": "object",
  "properties": {
    "order_number": {
      "type": "string",
      "description": "The order number, e.g. A1234"
    }
  },
  "required": ["order_number"]
}

Headers:

Authorization: Bearer your-endpoint-token

Write clear descriptions for the tool and for each parameter: the agent relies on them. Mention the tool in your prompt too, such as Before answering delivery questions, look up the order with get_order_status.

What your endpoint receives

When the agent uses a tool, we send a POST to its endpoint with a JSON body:

{
  "tool": "get_order_status",
  "arguments": { "order_number": "A1234" },
  "call": { "id": "8b0c6c5e-…", "agentId": "3f1e2d4a-…" }
}

Field	Description
`tool`	The function name
`arguments`	The arguments the agent collected, matching your JSON Schema
`call.id`	The call’s ID. It matches the post-call webhook and the dashboard’s Calls tab.
`call.agentId`	The voice agent’s ID

Headers: Content-Type: application/json, the headers you set, and the signature headers webhook-id, webhook-timestamp and webhook-signature. Your own headers can’t override the signature headers.

What to send back

Reply within 10 seconds. The response body, text or JSON, is what the agent learns, and the conversation carries on.

{ "status": "shipped", "carrier": "UPS", "eta": "Thursday" }

Your response	What the agent gets
`2xx` with a body	The body (the first 8,000 characters)
`2xx` with an empty body	`Done.`
`4xx` or `5xx`	An error with the HTTP status and your response body, so it can tell the caller
No response within 10 seconds, or unreachable	An error telling it to say it can’t do that right now

Keep responses short and to the point. Return only the facts the agent needs to say, in plain words or small JSON.

Verify requests

Every tool request is signed with the agent’s signing secret, so you can check it came from your agent. See Verify signatures.

Express

import express from "express";
import { Webhook } from "standardwebhooks";

const webhook = new Webhook(process.env.AGENT_SIGNING_SECRET); // whsec_…
const app = express();

app.post("/agent/orders", express.raw({ type: "application/json" }), async (req, res) => {
  let body;
  try {
    body = webhook.verify(req.body.toString(), req.headers); // throws if invalid or over 5 minutes old
  } catch {
    return res.status(401).send("Invalid signature");
  }
  const order = await findOrder(body.arguments.order_number);
  res.json(order ? { status: order.status, eta: order.eta } : { error: "No order with that number" });
});

No-code endpoints

Point a tool at a Zapier Catch Hook, a Make Custom webhook or an n8n Webhook node, and finish the automation with a response step (for example n8n’s Respond to Webhook) that returns what the agent should know. Keep the automation under 10 seconds.

See tool calls

Each call on the Calls tab shows how many tool calls it made. The transcript shows what the agent said with the results.

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Help

Built-in: End call

Add a custom tool

Example

What your endpoint receives

What to send back

Verify requests

No-code endpoints

See tool calls

​Built-in: End call

​Add a custom tool

​Example

​What your endpoint receives

​What to send back

​Verify requests

​No-code endpoints

​See tool calls

Built-in: End call

Add a custom tool

Example

What your endpoint receives

What to send back

Verify requests

No-code endpoints

See tool calls