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This guide walks you through the four REST calls it takes to answer your first phone call with an AI agent.
You’ll need a ThunderPhone account. Sign up is free and takes under a minute.

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Step 1: Get an API key

1

Log in

Open app.thunderphone.com.
2

Navigate to Keys

Click Settings → Keys.
3

Create a key

Click Create API Key, give it a name, and copy the sk_live_... value. The raw key is shown only once — store it in your secret manager immediately.
Throughout this guide, swap sk_live_YOUR_API_KEY with the value you just copied. The key identifies your organization automatically, so you never need to put an org id in URLs.

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Step 2: Create an agent

An agent defines how the AI handles conversations — prompt, voice, product tier, tools, and widget eligibility. 
curl -X POST https://api.thunderphone.com/v1/agents \
  -H "Authorization: Bearer sk_live_YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name":   "Customer Support",
    "prompt": "You are a friendly support agent for Acme Corp. Help with orders, returns, and product info. Be concise and helpful.",
    "voice":  "en-US-James1",
    "product": "spark"
  }'
Product tiers: spark for lowest latency, bolt for balanced, and storm-base / storm-extra for reasoning-heavy conversations. See Agents for the full comparison.

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Step 3: Provision a phone number

This call asks ThunderPhone’s demo pool for a number and assigns your new agent as the inbound handler. (To bring your own number from a VoIP provider, see VoIP connections instead.) 
# First provision
curl -X POST https://api.thunderphone.com/v1/phone-numbers \
  -H "Authorization: Bearer sk_live_YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"area_code": "415"}'

# Then assign the agent you created in Step 2
curl -X PATCH https://api.thunderphone.com/v1/phone-numbers/<id-from-previous> \
  -H "Authorization: Bearer sk_live_YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"inbound_agent_id": 12}'
Your new number starts in status="provisioning" and transitions to active within a few seconds; by the time you hang up your browser the number is ready to take calls.

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Step 4 (optional): Set up a webhook

For real-time events (dynamic call routing, post-call processing) add a webhook endpoint. Subscribe only to the events you need. 
curl -X POST https://api.thunderphone.com/v1/developer/webhook-endpoints \
  -H "Authorization: Bearer sk_live_YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "label":  "Prod webhook",
    "url":    "https://your-server.com/thunderphone-webhook",
    "events": ["telephony.incoming", "telephony.complete"]
  }'
The response contains a one-shot secret — copy it to your secret manager. Use that secret to verify the X-ThunderPhone-Signature header on incoming requests (see Webhooks overview).

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Step 5: Test your agent

Call the number you just provisioned. The agent picks up, introduces itself, and follows your prompt. Inspect the call after it ends: 
curl https://api.thunderphone.com/v1/calls \
  -H "Authorization: Bearer sk_live_YOUR_API_KEY"
Drill into a specific call to fetch the transcript and recording URL: 
curl https://api.thunderphone.com/v1/calls/{call_id}/transcript \
  -H "Authorization: Bearer sk_live_YOUR_API_KEY"
curl https://api.thunderphone.com/v1/calls/{call_id}/audio \
  -H "Authorization: Bearer sk_live_YOUR_API_KEY"

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Next steps

Add function tools

Let your agent call your APIs during a conversation.

Place outbound calls

Trigger calls from your own code.

Handle webhooks

React to call events in real time.

Full API reference

Every public endpoint, documented.