SLNG Voice Agent API examples

Working code for the agent lifecycle. For prompt design, tool configuration, and template variables, see Configuring voice agents.

Placeholders

Every snippet below uses these placeholders. Replace them before running the code.

Placeholder	Replace with
`SLNG_API_KEY`	An SLNG key from app.slng.ai/api-keys. Use it as the bearer token in the `Authorization` header.
`AGENT_ID` / `550e8400-e29b-41d4-a716-446655440000`	The agent’s UUID returned by `POST /v1/agents`
`region: "eu-central"`	A Voice Agents logical region. See Agent regions

Create an agent

const resp = await fetch("https://api.agents.slng.ai/v1/agents", {
  method: "POST",
  headers: {
    Authorization: "Bearer SLNG_API_KEY",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    name: "Appointment Reminder",
    system_prompt:
      "You are a friendly appointment reminder for {{clinic_name}}. " +
      "Confirm the patient upcoming visit or help them reschedule. " +
      "Keep responses to one or two sentences.",
    greeting: "Hi {{patient_name}}, this is a reminder from {{clinic_name}} about your upcoming appointment.",
    language: "en",
    region: "eu-central",
    models: {
      stt: "slng/deepgram/nova:3-en",
      llm: "groq/openai/gpt-oss-120b",
      tts: "slng/deepgram/aura:2-en",
      tts_voice: "aura-2-thalia-en",
    },
    template_defaults: {
      clinic_name: "Downtown Health Clinic",
      patient_name: "there",
    },
  }),
});

const agent = await resp.json();
console.log(agent.id);

import requests

resp = requests.post(
    "https://api.agents.slng.ai/v1/agents",
    headers={"Authorization": "Bearer SLNG_API_KEY"},
    json={
        "name": "Appointment Reminder",
        "system_prompt": (
            "You are a friendly appointment reminder for {{clinic_name}}. "
            "Confirm the patient upcoming visit or help them reschedule. "
            "Keep responses to one or two sentences."
        ),
        "greeting": "Hi {{patient_name}}, this is a reminder from {{clinic_name}} about your upcoming appointment.",
        "language": "en",
        "region": "eu-central",
        "models": {
            "stt": "slng/deepgram/nova:3-en",
            "llm": "groq/openai/gpt-oss-120b",
            "tts": "slng/deepgram/aura:2-en",
            "tts_voice": "aura-2-thalia-en",
        },
        "template_defaults": {
            "clinic_name": "Downtown Health Clinic",
            "patient_name": "there",
        },
    },
)

agent = resp.json()
print(agent["id"])

curl -X POST https://api.agents.slng.ai/v1/agents \
  -H "Authorization: Bearer SLNG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Appointment Reminder",
    "system_prompt": "You are a friendly appointment reminder for {{clinic_name}}. Confirm the patient upcoming visit or help them reschedule. Keep responses to one or two sentences.",
    "greeting": "Hi {{patient_name}}, this is a reminder from {{clinic_name}} about your upcoming appointment.",
    "language": "en",
    "region": "eu-central",
    "models": {
      "stt": "slng/deepgram/nova:3-en",
      "llm": "groq/openai/gpt-oss-120b",
      "tts": "slng/deepgram/aura:2-en",
      "tts_voice": "aura-2-thalia-en"
    },
    "template_defaults": {
      "clinic_name": "Downtown Health Clinic",
      "patient_name": "there"
    }
  }'

Test with a web session

Web sessions let you talk to your agent from a browser. No phone number or SIP trunk required. The response includes LiveKit credentials you can use with any LiveKit client SDK.

const resp = await fetch(
  `https://api.agents.slng.ai/v1/agents/${agent.id}/web-sessions`,
  {
    method: "POST",
    headers: {
      Authorization: "Bearer SLNG_API_KEY",
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      arguments: { patient_name: "Maria", clinic_name: "Greenfield Family Medicine" },
    }),
  },
);

const session = await resp.json();
// session.livekit_url:   WebSocket URL to connect to
// session.livekit_token: access token for the room
// session.room_name:     LiveKit room name
// session.call_id:       use this to look up the call later
// session.max_session_seconds: how long the session stays open

resp = requests.post(
    f"https://api.agents.slng.ai/v1/agents/{agent['id']}/web-sessions",
    headers={"Authorization": "Bearer SLNG_API_KEY"},
    json={
        "arguments": {"patient_name": "Maria", "clinic_name": "Greenfield Family Medicine"},
    },
)

session = resp.json()
# session["livekit_url"]:   WebSocket URL to connect to
# session["livekit_token"]: access token for the room
# session["room_name"]:     LiveKit room name
# session["call_id"]:       use this to look up the call later
# session["max_session_seconds"]: how long the session stays open

curl -X POST https://api.agents.slng.ai/v1/agents/AGENT_ID/web-sessions \
  -H "Authorization: Bearer SLNG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "participant_name": "Test user",
    "arguments": {
      "patient_name": "Maria"
    }
  }'

Both fields are optional. arguments overrides template_defaults on the agent, and participant_name sets a display name in the LiveKit room.

Update an agent

PATCH updates only the fields you send. Use PUT if you want to replace the entire configuration.

const resp = await fetch(
  `https://api.agents.slng.ai/v1/agents/${agent.id}`,
  {
    method: "PATCH",
    headers: {
      Authorization: "Bearer SLNG_API_KEY",
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      greeting: "Hello {{patient_name}}, thanks for picking up.",
      models: {
        stt: "slng/deepgram/nova:3-en",
        llm: "groq/openai/gpt-oss-120b",
        tts: "slng/deepgram/aura:2-en",
        tts_voice: "aura-2-thalia-en",
        llm_kwargs: { temperature: 0.3 },
      },
    }),
  },
);

const updated = await resp.json();

resp = requests.patch(
    f"https://api.agents.slng.ai/v1/agents/{agent['id']}",
    headers={"Authorization": "Bearer SLNG_API_KEY"},
    json={
        "greeting": "Hello {{patient_name}}, thanks for picking up.",
        "models": {
            "stt": "slng/deepgram/nova:3-en",
            "llm": "groq/openai/gpt-oss-120b",
            "tts": "slng/deepgram/aura:2-en",
            "tts_voice": "aura-2-thalia-en",
            "llm_kwargs": {"temperature": 0.3},
        },
    },
)

updated = resp.json()

curl -X PATCH https://api.agents.slng.ai/v1/agents/AGENT_ID \
  -H "Authorization: Bearer SLNG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "greeting": "Hello {{patient_name}}, thanks for picking up.",
    "models": {
      "stt": "slng/deepgram/nova:3-en",
      "llm": "groq/openai/gpt-oss-120b",
      "tts": "slng/deepgram/aura:2-en",
      "tts_voice": "aura-2-thalia-en",
      "llm_kwargs": { "temperature": 0.3 }
    }
  }'

Duplicate an agent

Use duplication when you want to copy an existing agent configuration as-is, including prompts, models, tools, template defaults, selected region, and outbound telephony settings. The duplicate does not copy call history or the inbound connection. After duplicating an agent:

Reconnect inbound routing if the duplicate should receive calls.
Verify the outbound trunk before dispatching calls.
Test the duplicate with a web session or a test call.

const duplicated = await fetch(
  `https://api.agents.slng.ai/v1/agents/${agent.id}/duplicate`,
  {
    method: "POST",
    headers: {
      Authorization: "Bearer SLNG_API_KEY",
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      name: `${agent.name} Copy`,
    }),
  },
).then((r) => r.json());

console.log(duplicated.id);

duplicated = requests.post(
    f"https://api.agents.slng.ai/v1/agents/{agent['id']}/duplicate",
    headers={"Authorization": "Bearer SLNG_API_KEY"},
    json={
        "name": f"{agent['name']} Copy",
    },
).json()

print(duplicated["id"])

curl -X POST https://api.agents.slng.ai/v1/agents/AGENT_ID/duplicate \
  -H "Authorization: Bearer SLNG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Appointment Reminder Copy"
  }'

List and inspect agents

// List all agents
const agents = await fetch("https://api.agents.slng.ai/v1/agents", {
  headers: { Authorization: "Bearer SLNG_API_KEY" },
}).then((r) => r.json());

for (const a of agents) {
  console.log(`${a.name} (${a.id})`);
}

// Get a single agent and check its template variables
const agent = await fetch(`https://api.agents.slng.ai/v1/agents/${agents[0].id}`, {
  headers: { Authorization: "Bearer SLNG_API_KEY" },
}).then((r) => r.json());

console.log(agent.template_variables);
// { clinic_name: { required: true, default: "Downtown Health Clinic" }, ... }

# List all agents
agents = requests.get(
    "https://api.agents.slng.ai/v1/agents",
    headers={"Authorization": "Bearer SLNG_API_KEY"},
).json()

for a in agents:
    print(f"{a['name']} ({a['id']})")

# Get a single agent and check its template variables
agent = requests.get(
    f"https://api.agents.slng.ai/v1/agents/{agents[0]['id']}",
    headers={"Authorization": "Bearer SLNG_API_KEY"},
).json()

print(agent["template_variables"])
# {"clinic_name": {"required": true, "default": "Downtown Health Clinic"}, ...}

Delete an agent

Returns 204 No Content on success.

await fetch(`https://api.agents.slng.ai/v1/agents/${agent.id}`, {
  method: "DELETE",
  headers: { Authorization: "Bearer SLNG_API_KEY" },
});

requests.delete(
    f"https://api.agents.slng.ai/v1/agents/{agent['id']}",
    headers={"Authorization": "Bearer SLNG_API_KEY"},
)

curl -X DELETE https://api.agents.slng.ai/v1/agents/AGENT_ID \
  -H "Authorization: Bearer SLNG_API_KEY"

Get started

Text-to-Speech

Speech-to-Text

Voice Agents

Integrations

SDKs & Tools

Reference

Placeholders

Create an agent

Test with a web session

Update an agent

Duplicate an agent

List and inspect agents

Delete an agent

​Placeholders

​Create an agent

​Test with a web session

​Update an agent

​Duplicate an agent

​List and inspect agents

​Delete an agent

Placeholders

Create an agent

Test with a web session

Update an agent

Duplicate an agent

List and inspect agents

Delete an agent