Phone & Voice

Two namespaces in one tool: /v1/phone/* for number intelligence + provisioning, /v1/voice/* for outbound AI calls. Pay per call in USDC. Any other path is refused before payment — the tool never reaches routes outside these two.

Phone numbers use E.164 format — + followed by country code and subscriber digits (US: +1 + 10 digits; UK: +44 + 10 digits; etc.). The examples below use <+E.164-number> as a placeholder — the LLM should substitute the actual number from the user's request, not copy the literal placeholder.

How to Call from MCP

const targetNumber = "<+E.164-number-from-user>"  // e.g. user said "call my doctor at 415-..."

// Lookup carrier + line type
blockrun_phone({ path: "phone/lookup", body: { phoneNumber: targetNumber } })

// Buy a 30-day US number
blockrun_phone({ path: "phone/numbers/buy", body: { country: "US", areaCode: "415" } })

// Outbound AI call (requires `from` — see below)
const r = await blockrun_phone({ path: "voice/call", body: {
  to: targetNumber,
  from: "<+E.164-number-you-own>",       // from phone/numbers/buy
  task: "Confirm appointment for Friday at 3pm with Dr. Wong.",
  voice: "june"
}})
// poll the result (free GET, no body)
blockrun_phone({ path: `voice/call/${r.call_id}` })

Endpoint Catalog

Phone intelligence + numbers (/v1/phone/*)

Outbound AI calls (/v1/voice/*)

from is REQUIRED and must be a number your wallet owns. Provision one first with phone/numbers/buy ($5, 30-day lease). 400 errors from voice/call are almost always missing from.

Voice Call Body Fields

Voice Presets

Worked Examples

1. Triage an inbound number for fraud

blockrun_phone({ path: "phone/lookup/fraud", body: { phoneNumber: "+14155550150" } })

Returns carrier, line type, SIM-swap indicator, call-forwarding state. Cost: $0.0510.

2. Spin up a US number with a 415 area code

blockrun_phone({ path: "phone/numbers/buy", body: { country: "US", areaCode: "415" } })
// returns { phoneNumber: "+14155550199", expires_at: "..." }

Best-effort area code match. Cost: $5.001 for 30 days.

3. Confirm an appointment via AI voice call

// Step 0 (one-time): provision a number you'll use as caller ID
const { phoneNumber: myNumber } = await blockrun_phone({
  path: "phone/numbers/buy", body: { country: "US", areaCode: "415" }
})  // $5.001, 30-day lease

// Step 1: place the call (from is REQUIRED)
const r = await blockrun_phone({ path: "voice/call", body: {
  to: "+14155550100",
  from: myNumber,
  task: "Call Dr. Wong's office. Confirm the appointment for Sarah Chen on Friday May 24th at 3pm. If the time isn't available, ask for the next opening on Friday afternoon and report back.",
  voice: "june",
  max_duration: 5,
  wait_for_greeting: true
}})
// returns { call_id: "call_abc..." } — call runs async

// Poll until done
while (true) {
  const status = await blockrun_phone({ path: `voice/call/${r.call_id}` })
  if (status.status === "completed") {
    console.log(status.summary, status.transcript)
    break
  }
  await new Promise(r => setTimeout(r, 5000))
}

Cost: $0.5410 flat for the call. Status polling is free.

4. List your wallet's leased numbers + release one

const { numbers } = await blockrun_phone({ path: "phone/numbers/list", body: {} })
// Release the oldest
await blockrun_phone({ path: "phone/numbers/release", body: { phoneNumber: numbers[0].phoneNumber } })

Best Practices

• Always include task context the AI can act on. "Confirm appointment" is vague; "Confirm Sarah Chen's appointment for Friday May 24 at 3pm with Dr. Wong" is actionable.
• Use wait_for_greeting: true for human-answered calls (most cases). Set to false for known-IVR / known-bot destinations to skip the greeting wait.
• max_duration is a hard cap — the call ends regardless of conversation state. Default 5 min covers most scripted tasks.
• from matters for trust** — using a provisioned BlockRun number you own (from numbers/buy) makes the call look less spammy than a random caller ID.

When NOT to Use

• High-volume autodialer / robocall workloads — pricing is per-call ($0.5410 each) which doesn't amortize like wholesale telephony
• Receiving inbound calls — numbers/buy provisions a number but inbound routing is not exposed via MCP; use Bland directly
• Two-way human-to-human calls — this is for AI-driven outbound; for real-time human bridging, use a SIP provider

Notes

• phone/lookup is cheap reconnaissance; phone/lookup/fraud is 5× the price but adds SIM-swap + call-forwarding signals you can't get from a basic carrier lookup
• Voice calls return immediately with a call_id; the call runs in the background. Always poll voice/call/{call_id} to get the transcript
• The poll endpoint is free — poll as often as you want, but every 5s is plenty
• Calls that fail upstream (recipient hangs up, no answer) still charge the flat $0.5410 — Bland's pricing model

Reference

• Phone endpoints: POST /v1/phone/*
• Voice endpoints: POST /v1/voice/call and GET /v1/voice/call/{call_id}
• Upstream: number intelligence + provisioning is internal; voice calls are Bland.ai