jambonz vs Twilio Programmable Voice API + MCP

jambonz

OpenAPI 3.1 and AsyncAPI documents, an llms.txt and Markdown pages cover the REST and WebSocket APIs, and session prices are public. No status page, security.txt or advisory was found, API keys carry no scopes, and the 2021 privacy policy says audio is never stored while the October 2026 release notes say support keeps call audio for a few days.

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.

jambonz

1. Send Authorization: Bearer <token> to https://api.jambonz.cloud/v1, the server in the OpenAPI files. The REST introduction page gives https://jambonz.cloud/api instead, so confirm the base URL with the operator
2. Create a call with from, to and either application_sid or call_hook. Do not retry a timed-out create without checking GET /Accounts/{AccountSid}/Calls first
3. Read ratelimit-remaining and ratelimit-reset on every response and stop when a 429 arrives
4. Append #rc=3&rp=5xx,ct to an application URL to turn on webhook retries. HTTP webhooks are not retried by default
5. Check the account has a carrier and speech credentials before dialling. jambonz does not supply numbers, minutes or speech services

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