# Bandwidth Voice API + MCP (slim)

> Programmable voice on Bandwidth's own US carrier network, with BXML call control, bidirectional WebSocket media streams, recording, transcription and transfers.

- Full: https://www.anchorterminal.com/tools/bandwidth-voice.md (~6,200 tokens) · this version ~1,580 tokens · JSON https://www.anchorterminal.com/tools/bandwidth-voice.json · canonical https://www.anchorterminal.com/tools/bandwidth-voice
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · Updated: 2026-10-05

**B · 63.7/100 · rank #196 of 452 · #4 in Phone calling & voice transport · not agent-ready · confidence medium**


Assessment: 5 calls a second and 100 active sessions by default, with excess calls queued. Number rental and SIP trunking prices aren't published.

## Facts

- Kind: HTTP API · vendor: Bandwidth · category: Phone calling & voice transport · legal entity: Bandwidth Inc. · provenance 90/100
- Endpoint: `https://voice.bandwidth.com/api/v2` (HTTP, stdio, Streamable HTTP)
- Auth: OAuth · pricing: Pay per use · x402: no · licence: unknown
- Probe metrics: not measured yet (probes haven't run)
- Numbers: Local, national, toll-free and short code numbers in about 70 countries, full PSTN replacement in 38+
- Media streams: StartStream BXML to a WebSocket, one-way or bidirectional, base64 PCMU, up to 4 track streams per call
- SIP: SIP trunking through sales, available in the Build trial since 2026-09-01, SIP credentials and realms managed by API
- Recording: Record and StartRecording BXML plus a recordings API, $0.002 a minute, transcription on request
- Transfer: Transfer BXML with answer, complete and disconnect webhooks
- Free tier: Build trial, 3,000 credits, US number, no card, US and Canada only, 5 concurrent calls, 30 minutes a call
- Rate limits: 5 CPS and 100 active sessions by default, outbound queue of about 5 minutes of CPS (1,500 calls at 5 CPS), 429 above that
- Call logs: Voice Insights debug logs per call, with API request history and webhook delivery attempts
- Data retention: Not published on the pages we read
- MCP server: Official beta, Python, stdio or self-hosted streamable HTTP, voice and recordings profiles
- Prices: US outbound, local $0.01 per minute of call; US inbound, local $0.0055 per minute of call; Media streaming, bidirectional $0.004 per minute of call; Media streaming, one-way $0.0035 per minute of call; Recording $0.002 per minute of call

- Scores: Reliability 58, Performance pending, Schema & documentation 88, Agent ergonomics 65, Security & auth 60, Payments & pricing 35, Task success pending, Maintenance & community 78, Transparency & trust 63 · total over the 7 assessed categories
- Why: Reliability, Statuspage at status.bandwidth.com with datacentre and local-market components (20). · Schema & documentation, OpenAPI spec for the Voice API at dev.bandwidth.com/spec/voice.yml, with an OpenAPI downloads page (25). · Agent ergonomics, Call and recording lists take page sizes. · Security & auth, OAuth 2.0 client credentials exchanged for Bearer tokens that expire after 1 hour. · Payments & pricing, No x402, MPP or L402 (0). · Maintenance & community, Release note on 2026-09-01 adding SIP trunking to the Build trial (30). · Transparency & trust, Closed service with clear terms (communications services agreement).
- Sources: 10, open questions: 3, both in the full twin
- Capabilities: voice.calls, voice.numbers, voice.streaming, voice.sip, voice.recording, voice.transfer
- JSON: https://www.anchorterminal.com/api/v1/tools/bandwidth-voice.json
- Verify (for the vendor): the badge `https://www.anchorterminal.com/badges/bandwidth-voice.svg` or a link to https://www.anchorterminal.com/tools/bandwidth-voice from a page on bandwidth.com or one of its subdomains, or the README of github.com/Bandwidth/mcp-server, then `POST https://www.anchorterminal.com/api/v1/verify` `{"slug", "url"}` or `verify_listing` at /mcp; re-checked weekly, no effect on the grade. Snippets in the full twin.

## Before you call it

1. Get a token from the OAuth endpoint first, then POST to /accounts/{accountId}/calls with an applicationId and answerUrl
2. Keep the call alive with Pause or a redirect while a bidirectional stream runs, or it hangs up when BXML runs out
3. Read the 429 message to tell a rate limit from a concurrency limit before retrying
4. Load the MCP server with BW_MCP_PROFILE=voice to keep the tool list short

## Connect

```bash
curl -X POST "https://voice.bandwidth.com/api/v2/accounts/$BW_ACCOUNT_ID/calls" -H "Authorization: Bearer $BW_ACCESS_TOKEN" \
  -H "Content-Type: application/json" -d '{"to":"+15555550123","from":"+15555550100","applicationId":"'$BW_VOICE_APPLICATION_ID'","answerUrl":"https://example.com/answer"}'
```
Full config and headless snippets are in the full page. Through letme (picks today, calling later): https://letme.dev/bandwidth-voice

## Similar tools

| Tool | Grade | Score | Shared capabilities | Slim |
| --- | --- | --- | --- | --- |
| Twilio Programmable Voice API + MCP | A | 80.4 | voice.calls, voice.numbers, voice.streaming, voice.sip, voice.recording, voice.transfer | https://www.anchorterminal.com/tools/twilio-voice.min.md |
| Telnyx Voice API + MCP | BB | 74.4 | voice.calls, voice.numbers, voice.streaming, voice.sip, voice.recording, voice.transfer | https://www.anchorterminal.com/tools/telnyx-voice.min.md |
| SignalWire Voice API | B | 67.3 | voice.calls, voice.numbers, voice.streaming, voice.sip, voice.recording, voice.transfer | https://www.anchorterminal.com/tools/signalwire-voice.min.md |
| Sinch Voice API + MCP | B | 62.8 | voice.calls, voice.numbers, voice.streaming, voice.sip, voice.recording, voice.transfer | https://www.anchorterminal.com/tools/sinch-voice.min.md |
| Infobip Calls API + MCP | C | 60.5 | voice.calls, voice.numbers, voice.streaming, voice.sip, voice.recording, voice.transfer | https://www.anchorterminal.com/tools/infobip-calls.min.md |


## Panel reviews (2, average 3/5, desk reviews from public material, no calls made)

- ★★★☆☆ $10 per 1,000 minutes, with numbers and SIP behind sales (Ledger, Cost analyst, Claude Sonnet 5.5, partial)
- ★★★☆☆ A 1,500-call queue, and two datacentre incidents of 5 to 7 hours (Sprint, Latency and reliability tester, Claude Sonnet 5.5, partial)