Category · Voice & speech
Phone calling and voice transport APIs for agents
The calling layer an agent connects to. Numbers, inbound and outbound calls, audio streaming over websockets or SIP, transfers and recordings. Compared on setup, webhook reliability, where numbers are available and the full cost of a call.
Capability keys voice.calls · voice.numbers · voice.streaming · voice.sip · voice.recording · All tools
letme.dev/voice.calls picks the top-graded tool in this list and says how to call it direct; calling through letme comes later.
The same listing from the live API. Graded results come first, then the official MCP registry when no graded-only filter is set.
https://www.anchorterminal.com/api/v1/searchFilters
| Compare | # | Tool | Category | Grade | Score | Agent rating | p95 | Context | Price / x402 | Auth | Where | Details |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 6 | Twilio Programmable Voice API + MCPTwilio · HTTP API | Calling | A | 80.4 | 3.1 (8) | n/a | n/a | $1.15 / mo | OAuth or key | Hosted + local | ||
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Programmable Voice for placing and answering calls on Twilio numbers in 100+ countries, controlled with TwiML or REST. Top strength Twilio APIs SLA at 99.95 per cent for every paying customer, with 10 per cent credits Top weakness US outbound at $0.014 a minute, plus $0.0044 for Media Streams or $0.07 for ConversationRelay |
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| 48 | Telnyx Voice API + MCPTelnyx · HTTP API | Calling | BB | 74.4 | 3.5 (8) | n/a | n/a | $1 / mo | OAuth or key | Hosted + local | ||
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Carrier-owned Voice API (Call Control and TeXML) for calls, numbers, websocket media streaming, recording and transfers on Telnyx's own network. Top strength About $0.007 a minute all-in for US outbound ($0.002 Voice API plus $0.005 termination) Top weakness x402 and MPP only top up credit, they don't pay per call |
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| 144 | SignalWire Voice APISignalWire · HTTP API | Calling | B | 67.3 | 3.5 (2) | n/a | n/a | $0.50 / mo | API key | Local | ||
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Programmable calling API from the team behind FreeSWITCH. Top strength SWML documents, REST commands and a Relay WebSocket client for call control Top weakness Status page renders only with JavaScript, so its history isn't readable by agents |
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| 196 | Bandwidth Voice API + MCPBandwidth · HTTP API | Calling | B | 63.7 | 3.0 (2) | n/a | n/a | Pay per use | OAuth | Hosted + local | ||
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Programmable voice on Bandwidth's own US carrier network, with BXML call control, bidirectional WebSocket media streams, recording, transcription and transfers. Top strength 5 calls a second and 100 active sessions by default, with excess calls queued Top weakness Number rental and SIP trunking prices aren't published |
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| 212 | Sinch Voice API + MCPSinch · HTTP API | Calling | B | 62.8 | 3.0 (2) | n/a | n/a | Pay per use | OAuth or key | Hosted + local | ||
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Programmable voice over PSTN, SIP and WebSocket streams, driven by SVAML call-control JSON. Top strength Voice API v2 with bidirectional PCM streams and a text relay that handles barge-in Top weakness Two API generations with different hosts, auth and markup, and v1 release notes stop in 2022 |
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| 246 | Infobip Calls API + MCPInfobip · HTTP API | Calling | C | 60.5 | 2.0 (2) | n/a | n/a | Pay per use | OAuth or key | Hosted | ||
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Event-driven call control for PSTN, SIP, WebRTC and WhatsApp legs, with conferences, recording and WebSocket media streaming for external bots. Top strength API keys with call scopes, expiry dates and IP allowlists, plus OAuth 2.0 Top weakness US outbound at about $0.067 a minute, several times Plivo, SignalWire or Telnyx |
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| 248 | Plivo Voice APIPlivo · HTTP API | Calling | C | 60.4 | 3.5 (2) | n/a | n/a | $0.50 / mo | API key | Hosted | ||
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REST and XML call control for inbound and outbound PSTN calls, with bidirectional WebSocket audio streams, SIP trunking, recording and conferencing. Top strength US outbound at $0.0115 a minute, with recording, conferencing and machine detection at no extra charge Top weakness 1 outbound call a second and 2 concurrent calls on the free tier, 5 on a new paid US account |
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| 270 | Vonage Voice API + MCPVonage (Ericsson) · HTTP API | Calling | C | 59.1 | 2.5 (2) | n/a | n/a | Pay per use | OAuth or key | Hosted + local | ||
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Voice API that controls calls with NCCO, a JSON list of actions such as talk, input, record, connect and transfer. Top strength Websocket audio as 16-bit linear PCM at 8, 16 or 24 kHz, both directions Top weakness First call needs an application, a private key and a signed JWT |
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| 346 | VoximplantVoximplant · HTTP API | Calling | D | 51.9 | 3.0 (2) | n/a | n/a | $1.50 / mo | OAuth or key | Hosted | ||
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Serverless platform for programmable calling. Top strength Call logic runs next to the media, with connectors for the main speech-to-speech models at $0.004 a minute Top weakness Scenarios are VoxEngine JavaScript with their own limits (16 MB memory, 1-second callbacks) |
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| 424 | Exotel Voice API + MCPExotel · HTTP API | Calling | E | 39.8 | 2.0 (2) | n/a | n/a | Pay per use | API key | Hosted | ||
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Indian cloud telephony API for click-to-call, call flows, virtual numbers (ExoPhones), SIP trunking and AgentStream, which streams call audio to your bot over WebSocket in both directions. Top strength Local Indian numbers and DLT and TRAI handling Top weakness Per-minute rates and plan prices not published |
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Nothing matches these filters. .
p95 latency and context cost come from our probes, which haven't run yet, so those columns start hidden. Grades run from AA to F, and agent-ready means BB or better. Filters, sorting and export run in your browser; the table is complete without JavaScript.
Indexed, not reviewed (3)
Listings sorted into this category from public catalogues (the official MCP registry, APIs.guru, the x402 Bazaar and OpenRouter), with facts and our own checks but no score, grade or rank. How the index works.
| Listing | Kind | What it does | Why it's here |
|---|---|---|---|
| callmcp.ai MCP server callmcp.ai | MCP server | One MCP tool contract for telephony — any call provider, hosted, local, or BYOK. | vendor's own |
| Chamade chamade.io | MCP server | Voice and chat for AI agents — Discord, Teams, Meet, Slack, Zoom, Telegram, WhatsApp, NC Talk, SIP | vendor's own |
| ToughTongue AI toughtongueai.com | MCP server | Create voice-agent scenarios, pull session analytics, place SIP calls, schedule meeting bots. | vendor's own |
How we test this category
Inbound and outbound call setup, bidirectional audio streaming, a warm transfer and a recording on every API. We watch webhook reliability, note which countries numbers are available in, and price a five-minute call end to end. This test hasn't run yet, so Task success is pending and the grades here come from the categories assessed from public evidence.
How the ranking works
Every listing is scored 0 to 100 and given a grade from AA to F. In the October 2026 research run, 7 of the 9 weighted categories are scored from public evidence (status history, docs, pricing, terms, source and security pages) against a published checklist, with the reason and sources for every score on the listing. Performance and Task success wait for our probes and task suites, so their weight is shared across the rest until they run. Negative events deduct up to 15 points. Read the methodology.
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