Bandwidth Voice API + MCP vs jambonz

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.

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.

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

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