Dispatch outbound calls

Dispatching a call tells an agent to dial a number now. The agent places the call through its outbound connection, so the caller ID comes from that connection’s pool rather than from the request.

Prerequisites

Before you begin:

An outbound connection attached to the agent. Without one, dispatch fails. See Place calls from an agent.
The agent’s ID, from the create response or the project page.
An SLNG key for the API path. See How to set up.

Place one call

Dashboard
API

Open the test panel

Open the project and click Test agent. The panel opens on the Web session channel.

The Test agent panel with the Channel set to Web session and an Outbound call option — The Test agent panel. Switch the channel to Outbound call.

Switch to Outbound call

Set the Channel to Outbound call. A Number to call field appears. If the panel says telephony setup is needed, the agent has no outbound connection attached.

The Test agent panel in outbound call mode showing the Number to call field — The Outbound call channel, with a field for the number to call.

Enter the number and start the call

Enter the destination under Number to call in E.164 format and click Start call. The agent dials while you watch the transcript.

The Test agent panel with a number entered and the Start call button — A number entered and ready. Start call places the outbound call.

Use this to check an agent before you automate it. For anything repeated, use the API.

Send the destination number to the agent’s calls endpoint.

Request

curl -X POST https://api.agents.slng.ai/v1/agents/$AGENT_ID/calls \
  -H "Authorization: Bearer $SLNG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "phone_number": "+14155551234" }'

Response

{
  "call_id": "7c1d9f02-4b6a-4e18-9d3c-2a5f8b0e6417",
  "message": "Call dispatched successfully"
}

The response returns as soon as the call is dispatched, not when it is answered. Keep the call_id to look the call up later.

Personalize each call

If the agent’s system prompt or greeting uses {{variable}} placeholders, pass values for them in arguments. They override any defaults set on the agent, and the rendered prompt is stored with the call record.

Request

curl -X POST https://api.agents.slng.ai/v1/agents/$AGENT_ID/calls \
  -H "Authorization: Bearer $SLNG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "phone_number": "+14155551234",
    "arguments": {
      "customer_name": "Bruce",
      "company_name": "Wayne Enterprises"
    }
  }'

Values are strings, and the payload is bounded:

Limit	Value
Keys per request	32
Key length	64 characters
Value length	1024 characters
All values combined	8192 characters

The request rejects anything it does not recognize, so a misspelled field name returns an error rather than being ignored.

Dispatch calls from a list

The API accepts one call per request. When you process a contact list, control the request rate and retry 429 Too Many Requests responses. Limiting concurrent requests does not control how many requests you send within the rate-limit window. This example sends calls sequentially, waits between contacts, and honors the Retry-After header before retrying a rate-limited request. Set DISPATCH_INTERVAL_MS for the rate limit applied to your account.

dispatch-list.mjs

const BASE_URL = "https://api.agents.slng.ai";

const wait = (milliseconds) =>
  new Promise((resolve) => setTimeout(resolve, milliseconds));

async function dispatchCall(agentId, phoneNumber, args = {}, maxRetries = 3) {
  for (let attempt = 0; ; attempt += 1) {
    const response = await fetch(`${BASE_URL}/v1/agents/${agentId}/calls`, {
      method: "POST",
      headers: {
        Authorization: `Bearer ${process.env.SLNG_API_KEY}`,
        "Content-Type": "application/json",
      },
      body: JSON.stringify({ phone_number: phoneNumber, arguments: args }),
    });

    if (response.ok) return response.json();

    if (response.status === 429 && attempt < maxRetries) {
      const retryAfter = Number(response.headers.get("retry-after"));
      await wait((Number.isFinite(retryAfter) ? retryAfter : 1) * 1000);
      continue;
    }

    const error = await response.json().catch(() => ({}));
    const detail =
      typeof error.detail === "string"
        ? error.detail
        : JSON.stringify(error.detail ?? error);
    throw new Error(detail || `Dispatch failed: ${response.status}`);
  }
}

async function dispatchList(agentId, contacts, intervalMs = 1000) {
  const results = [];

  for (const [index, contact] of contacts.entries()) {
    try {
      const value = await dispatchCall(agentId, contact.phone, contact.args);
      results.push({ phone: contact.phone, status: "fulfilled", value });
    } catch (error) {
      const reason = error instanceof Error ? error.message : String(error);
      results.push({ phone: contact.phone, status: "rejected", reason });
    }

    if (index < contacts.length - 1) await wait(intervalMs);
  }

  return results;
}

const contacts = [
  { phone: "+14155551234", args: { customer_name: "Bruce" } },
  { phone: "+14155559876", args: { customer_name: "Lucius" } },
];

if (!process.env.SLNG_API_KEY || !process.env.AGENT_ID) {
  throw new Error("Set SLNG_API_KEY and AGENT_ID before running this script.");
}

const intervalMs = Number(process.env.DISPATCH_INTERVAL_MS ?? 1000);
if (!Number.isFinite(intervalMs) || intervalMs < 0) {
  throw new Error("DISPATCH_INTERVAL_MS must be a non-negative number.");
}

const results = await dispatchList(process.env.AGENT_ID, contacts, intervalMs);
console.dir(results, { depth: null });

Run the script with your key and agent ID:

SLNG_API_KEY=your-key AGENT_ID=your-agent-id node dispatch-list.mjs

A failed contact does not stop the list. Review entries with a rejected status, fix the cause, then retry only those contacts.

Follow the call

Each dispatched call becomes a record you can read back: its status, the arguments you passed, the prompt after those arguments were filled in, and the transcript once the call ends. See Observability and usage.

Next steps

Receive calls on a number if callers also dial the agent.

Get started

Regions

Execution layer

Agent Builder

Models

Integrate

Prerequisites

Place one call

Personalize each call

Dispatch calls from a list

Follow the call

Next steps

​Prerequisites

​Place one call

​Personalize each call

​Dispatch calls from a list

​Follow the call

​Next steps

Prerequisites

Place one call

Personalize each call

Dispatch calls from a list

Follow the call

Next steps