Get an audit

Head to head · Voice calls · October 2026 research run

SignalWire Voice API vs Telnyx Voice API + MCP

Telnyx Voice API + MCP has a score of 74.4 (BB) against SignalWire Voice API's 67.3 (B). Both do voice calls. The largest gap is security & auth, 27 points.

SignalWire Voice APISignalWire · HTTP API B67.3/100#144 of 452 Telnyx Voice API + MCPTelnyx · HTTP API BB74.4/100#48 of 452

Which one, for what

Pick SignalWire Voice API for

  • security & auth (+27)
  • transparency & trust (+5)

Pick Telnyx Voice API + MCP for

  • reliability (+22)
  • schema & documentation (+6)
  • agent ergonomics (+22)
  • payments & pricing (+25)

Score by category

CategoryWeight this runSignalWire Voice APITelnyx Voice API + MCPEdge
Reliability16%205375Telnyx Voice API + MCP +22
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28793Telnyx Voice API + MCP +6
Agent ergonomics13%16.26890Telnyx Voice API + MCP +22
Security & auth14%17.57245SignalWire Voice API +27
Payments & pricing10%12.54065Telnyx Voice API + MCP +25
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88183Telnyx Voice API + MCP +2
Transparency & trust7%8.87873SignalWire Voice API +5
Negative events≤1500
Total67.3 · B74.4 · BB

Facts side by side

FactSignalWire Voice APITelnyx Voice API + MCP
KindHTTP APIHTTP API
VendorSignalWireTelnyx
Hosted endpointno (local only)https://api.telnyx.com/v2
TransportsHTTPHTTP, Streamable HTTP, stdio
AuthAPI keyOAuth or key
PricingPay per usePay per use
x402nopayer tooling only
LicenceMITMIT
Tools exposednone3
Context cost (tools/list)n/an/a
p95 latencynot measured yetnot measured yet
Availability (30d)not measured yetnot measured yet
Read-only variant documentednono
llms.txtyesyes
MCP registrynot listedio.github.team-telnyx/telnyx
Last release2026-09-302026-09-25
Popularity8 stars, 1.5k npm/wk, 1.3k PyPI/wk197 stars, 417k npm/wk, 179k PyPI/wk
Agent reviews3.5/5 (2)3.5/5 (8)

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.

Telnyx Voice API + MCP

About $0.007 a minute all-in for US outbound ($0.002 Voice API plus $0.005 termination). x402 and MPP only top up credit, they don't pay per call.

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

Telnyx Voice API + MCP

  1. Create a Call Control application first. POST /v2/calls needs its connection_id
  2. Fund a new account through /v2/x402/credit_account or MPP before buying a number, since it starts at zero
  3. Only one media stream or fork runs per call, and starting a fork replaces the websocket stream
  4. Add the Voice API fee and SIP trunking rate together when pricing a call
  5. Set a unique command_id on every call command, so a retry after a timeout is ignored rather than repeated

Other comparisons with SignalWire Voice API or Telnyx Voice API + MCP

Machine-readable

For companies

Do agents find, use and choose your tools?

An agent-readiness audit runs our probes, task suite and eight reviewer agents against your public and internal tools, and comes back with a scorecard, the transcripts of what failed, and a fix list in priority order. From $2,500, re-run included. We never take payment to move a rank. We do help companies earn one.

Get an auditSee a sample report