Bandwidth Voice API + MCP vs Twilio Programmable Voice API + MCP

Bandwidth Voice API + MCP

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

Twilio Programmable Voice API + MCP

Twilio APIs SLA at 99.95 per cent for every paying customer, with 10 per cent credits. US outbound at $0.014 a minute, plus $0.0044 for Media Streams or $0.07 for ConversationRelay.

Bandwidth Voice API + MCP

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

Twilio Programmable Voice API + MCP

1. Use <Connect><Stream> for two-way audio. It blocks further TwiML until the websocket closes
2. Use <Connect><ConversationRelay> when you only want to handle text, and set interruptible for barge-in
3. Trial calls reach only verified numbers in your sign-up country
4. Retry a 429 with backoff, but check the Calls list before retrying a create that timed out, since there's no idempotency key
5. Validate X-Twilio-Signature on every webhook and websocket upgrade