AI Phone Calls with StablePhone

Make AI-powered phone calls, buy phone numbers, and get transcripts via x402 payments at https://stablephone.dev.

Setup

See rules/getting-started.md for installation and wallet setup.

Quick Reference

Task	Endpoint	Price
Make a call	`https://stablephone.dev/api/call`	$0.54
Check call status	`GET https://stablephone.dev/api/call/{call_id}`	Free
Buy phone number	`https://stablephone.dev/api/number`	$20.00
Top up number (30d)	`https://stablephone.dev/api/number/topup`	$15.00
List your numbers	`GET https://stablephone.dev/api/numbers`	Free
iMessage/FaceTime lookup	`https://stablephone.dev/api/lookup`	$0.05
Lookup status	`GET https://stablephone.dev/api/lookup/status?token=...`	Free

Make a Call

npx agentcash@latest fetch https://stablephone.dev/api/call -m POST -b '{
  "phone_number": "+14155551234",
  "task": "Call this person and ask if they are available for a meeting tomorrow at 2pm. Be polite and professional."
}'

Required:

phone_number — E.164 format (e.g. +14155551234)
task — instructions for the AI agent (what to say, how to behave)

Optional:

from — outbound caller ID (must be an active StablePhone number)
first_sentence — specific opening line
voice — voice preset (see Voice Options below)
max_duration — max call length in minutes (1-30, default 5)
wait_for_greeting — wait for recipient to speak first (default false)
record — record call audio (default true)
model — "base" (default, best quality) or "turbo" (lowest latency)
transfer_phone_number — number to transfer to if caller requests a human
voicemail_action — "hangup" (default), "leave_message", or "ignore"
voicemail_message — message to leave (required when action is "leave_message")
metadata — custom key-value data to attach

Check Call Status

Poll until completed is true:

npx agentcash@latest fetch https://stablephone.dev/api/call/{call_id}

Response fields:

status — call status
completed — boolean, true when call is done
answered_by — "human", "voicemail", or "no_answer"
call_length — duration in seconds
summary — AI-generated call summary
transcript — full text transcript
transcripts — array of timestamped transcript segments
recording_url — URL to call recording
price — actual cost

Poll every 5-10 seconds. Calls typically complete in 1-5 minutes depending on max_duration.

Voice Options

Voice	Description
`nat`	American female (default)
`josh`	Articulate American male
`maya`	Young American female, soft
`june`	American female
`paige`	Calm, soft-tone female
`derek`	Soft and engaging male
`florian`	German male

Buy a Phone Number

Buy a number to use as outbound caller ID:

npx agentcash@latest fetch https://stablephone.dev/api/number -m POST -b '{"area_code": "415", "country_code": "US"}'

Optional:

area_code — 3-digit US/CA area code (random if omitted)
country_code — "US" (default) or "CA"

Numbers expire after 30 days. Top up to extend.

Top Up a Number

npx agentcash@latest fetch https://stablephone.dev/api/number/topup -m POST -b '{"phone_number": "+14155551234"}'

Extends by 30 days from current expiry. Top-ups stack. Anyone can top up any number.

List Your Numbers

Uses SIWX auth (wallet from auth header):

npx agentcash@latest fetch https://stablephone.dev/api/numbers

iMessage/FaceTime Lookup

Check if a phone number has iMessage or FaceTime. The lookup is async (30-90 seconds).

Step 1: Start the lookup (paid, $0.05)

npx agentcash@latest fetch https://stablephone.dev/api/lookup -m POST -b '{"phone_number": "+14155551234"}'

Returns 202 with {"token": "jwt..."}.

Step 2: Poll for results (SIWX, free)

npx agentcash@latest fetch "https://stablephone.dev/api/lookup/status?token=JWT_TOKEN"

Poll every 3-5 seconds until status is "complete".

Response when complete:

{
  "status": "complete",
  "phone_number": "+1...",
  "imessage": "available|unavailable|unknown",
  "facetime": "available|unavailable|unknown|pending",
  "carrier": {"carrier": "...", "number_type": "..."},
  "country": {"name": "...", "iso2": "...", "flag": "..."}
}

Notes:

"unknown" means the number exists but status can't be determined (likely landline/VoIP)
Token expires after 60 minutes
Same number within ~1 hour reuses cached result

Workflows

Quick Call

(Optional) Check balance: npx agentcash@latest balance
Make call with task instructions
Poll status until completed
Review transcript and summary

npx agentcash@latest fetch https://stablephone.dev/api/call -m POST -b '{
  "phone_number": "+14155551234",
  "task": "Ask if the business is open on weekends and what their hours are."
}'

Leave a Voicemail

npx agentcash@latest fetch https://stablephone.dev/api/call -m POST -b '{
  "phone_number": "+14155551234",
  "task": "Leave a voicemail about the appointment.",
  "voicemail_action": "leave_message",
  "voicemail_message": "Hi, this is a reminder about your appointment tomorrow at 3pm. Please call back to confirm."
}'

For natural voicemail delivery, use "voicemail_action": "ignore" which bypasses detection and lets the AI speak naturally into the voicemail system.

Call with Transfer

npx agentcash@latest fetch https://stablephone.dev/api/call -m POST -b '{
  "phone_number": "+14155551234",
  "task": "Qualify this lead. Ask about their budget and timeline. If they are interested, offer to transfer to a sales rep.",
  "transfer_phone_number": "+14155559999",
  "voice": "josh",
  "max_duration": 10
}'

Set Up Dedicated Number

Buy a phone number ($20)
Use it as caller ID for outbound calls
Top up before expiry ($15/30 days)

npx agentcash@latest fetch https://stablephone.dev/api/number -m POST -b '{"area_code": "212", "country_code": "US"}'

Then use it as from:

npx agentcash@latest fetch https://stablephone.dev/api/call -m POST -b '{
  "phone_number": "+14155551234",
  "from": "+12125551234",
  "task": "Confirm the reservation for Friday at 7pm."
}'

Cost Estimation

Task	Cost
Single call	$0.54
Call + dedicated number	$20.54
Monthly number maintenance	$15.00
10 calls/month + number	$20.00 + $5.40 = $25.40 first month

phone-calls