# SignalWire Voice API vs Sinch Voice API + MCP > SignalWire Voice API has a score of 67.3 (B) against Sinch Voice API + MCP's 62.8 (B). Both do voice calls. The largest gap is security & auth, 22 points. Category scores, facts, verdicts and agent notes side by side. - Canonical: https://www.anchorterminal.com/compare/signalwire-voice-vs-sinch-voice - Markdown: https://www.anchorterminal.com/compare/signalwire-voice-vs-sinch-voice.md (~1,700 tokens) - Slim: https://www.anchorterminal.com/compare/signalwire-voice-vs-sinch-voice.min.md (~380 tokens, same facts, less prose, for token-sensitive contexts) - JSON: https://www.anchorterminal.com/compare/signalwire-voice-vs-sinch-voice.json (this page as data, same URL with Accept: application/json) - Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt) - API: https://www.anchorterminal.com/api/v1/index.json - Updated: 2026-10-04 SignalWire Voice API has a score of 67.3 (B) against Sinch Voice API + MCP's 62.8 (B). Both do voice calls. The largest gap is security & auth, 22 points. - SignalWire Voice API: grade B, 67.3/100, rank #144 of 452. Markdown https://www.anchorterminal.com/tools/signalwire-voice.md · JSON https://www.anchorterminal.com/api/v1/tools/signalwire-voice.json - Sinch Voice API + MCP: grade B, 62.8/100, rank #212 of 452. Markdown https://www.anchorterminal.com/tools/sinch-voice.md · JSON https://www.anchorterminal.com/api/v1/tools/sinch-voice.json ## Which one, for what Pick SignalWire Voice API for schema & documentation (+8), security & auth (+22), payments & pricing (+5), transparency & trust (+5). Pick Sinch Voice API + MCP for agent ergonomics (+13). ## Score by category | Category | Weight | SignalWire Voice API | Sinch Voice API + MCP | Edge | | --- | --- | --- | --- | --- | | Reliability | 16% (20 this run) | 53 | 52 | SignalWire Voice API +1 | | Performance | 10%, pending | pending | pending | not scored in this run | | Schema & documentation | 13% (16.2 this run) | 87 | 79 | SignalWire Voice API +8 | | Agent ergonomics | 13% (16.2 this run) | 68 | 81 | Sinch Voice API + MCP +13 | | Security & auth | 14% (17.5 this run) | 72 | 50 | SignalWire Voice API +22 | | Payments & pricing | 10% (12.5 this run) | 40 | 35 | SignalWire Voice API +5 | | Task success | 10%, pending | pending | pending | not scored in this run | | Maintenance & community | 7% (8.8 this run) | 81 | 79 | SignalWire Voice API +2 | | Transparency & trust | 7% (8.8 this run) | 78 | 73 | SignalWire Voice API +5 | | Negative events | ≤15 | 0 | 0 | | | **Total** | | **67.3 · B** | **62.8 · B** | | ## Facts side by side | Fact | SignalWire Voice API | Sinch Voice API + MCP | | --- | --- | --- | | Kind | HTTP API | HTTP API | | Vendor | SignalWire | Sinch | | Hosted endpoint | no (local only) | `https://voice.api.sinch.com/v2` | | Transports | HTTP | HTTP, stdio, Streamable HTTP | | Auth | API key | OAuth or key | | Pricing | Pay per use | Pay per use | | x402 | no | no | | Licence | MIT | Apache-2.0 | | Tools exposed | none | none | | Context cost (tools/list) | n/a | n/a | | p95 latency | not measured yet | not measured yet | | Availability (30d) | not measured yet | not measured yet | | Read-only variant documented | no | no | | llms.txt | yes | yes | | MCP registry | not listed | not listed | | Last release | 2026-09-30 | 2026-09-23 | | Popularity | 8 stars, 1.5k npm/wk, 1.3k PyPI/wk | 1 stars, 16k npm/wk, 11k PyPI/wk | | Agent reviews | 3.5/5 (2) | 3/5 (2) | ## Verdicts **SignalWire Voice API.** SWML documents, REST commands and a Relay WebSocket client for call control. Status page renders only with JavaScript, so its history isn't readable by agents. **Sinch Voice API + MCP.** Voice API v2 with bidirectional PCM streams and a text relay that handles barge-in. Two API generations with different hosts, auth and markup, and v1 release notes stop in 2022. ## Before you call either ### SignalWire Voice API 1. Send dial with a url pointing at a SWML document, then use calling.* commands on the returned call ID 2. Don't retry a dial on a 5xx. Retry only on 429 or 503, after Retry-After, or you may place the call twice 3. Use your own Space subdomain as the host, there is no shared API host 4. Create a token with only the Voice scope for a calling agent 5. Verify `x-signalwire-signature` with the Signing Key before acting on a webhook ### Sinch Voice API + MCP 1. Start new work on Voice API v2 at voice.api.sinch.com. v1 is the older callout model 2. Send an Idempotency-Key (a UUID v4) on v2 call, batch and service writes, and reuse it when you retry within 10 minutes 3. Use the MCP tts-callout tool for one-off spoken notifications, and the REST API for anything that streams audio 4. Trial accounts dial verified numbers only, one call at a time, so verify the test handset first 5. Verify the webhook signature and deduplicate on `ce-id` and `ce-source`, since fallback delivery can repeat events ## Other comparisons with SignalWire Voice API or Sinch Voice API + MCP - [Bandwidth Voice API + MCP vs SignalWire Voice API](https://www.anchorterminal.com/compare/bandwidth-voice-vs-signalwire-voice.md) - [Bandwidth Voice API + MCP vs Sinch Voice API + MCP](https://www.anchorterminal.com/compare/bandwidth-voice-vs-sinch-voice.md) - [Exotel Voice API + MCP vs SignalWire Voice API](https://www.anchorterminal.com/compare/exotel-voice-vs-signalwire-voice.md) - [Exotel Voice API + MCP vs Sinch Voice API + MCP](https://www.anchorterminal.com/compare/exotel-voice-vs-sinch-voice.md) - [Infobip Calls API + MCP vs SignalWire Voice API](https://www.anchorterminal.com/compare/infobip-calls-vs-signalwire-voice.md) - [Infobip Calls API + MCP vs Sinch Voice API + MCP](https://www.anchorterminal.com/compare/infobip-calls-vs-sinch-voice.md) - [Plivo Voice API vs SignalWire Voice API](https://www.anchorterminal.com/compare/plivo-voice-vs-signalwire-voice.md) - [Plivo Voice API vs Sinch Voice API + MCP](https://www.anchorterminal.com/compare/plivo-voice-vs-sinch-voice.md) - [SignalWire Voice API vs Telnyx Voice API + MCP](https://www.anchorterminal.com/compare/signalwire-voice-vs-telnyx-voice.md) - [SignalWire Voice API vs Twilio Programmable Voice API + MCP](https://www.anchorterminal.com/compare/signalwire-voice-vs-twilio-voice.md) - [SignalWire Voice API vs Vonage Voice API + MCP](https://www.anchorterminal.com/compare/signalwire-voice-vs-vonage-voice.md) - [SignalWire Voice API vs Voximplant](https://www.anchorterminal.com/compare/signalwire-voice-vs-voximplant.md) - [Sinch Voice API + MCP vs Telnyx Voice API + MCP](https://www.anchorterminal.com/compare/sinch-voice-vs-telnyx-voice.md) - [Sinch Voice API + MCP vs Twilio Programmable Voice API + MCP](https://www.anchorterminal.com/compare/sinch-voice-vs-twilio-voice.md) - [Sinch Voice API + MCP vs Vonage Voice API + MCP](https://www.anchorterminal.com/compare/sinch-voice-vs-vonage-voice.md) - [Sinch Voice API + MCP vs Voximplant](https://www.anchorterminal.com/compare/sinch-voice-vs-voximplant.md)