Fonoster MCP Server

Build a programmable telecommunications stack for connecting telephony services with the Internet via a cloud-based utility.

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What is the Fonoster MCP server?

Build a programmable telecommunications stack for connecting telephony services with the Internet via a cloud-based utility. That is what the fonoster mcp server brings to an AI assistant: the same capability, reachable through the Model Context Protocol rather than a separate app or dashboard.

The short version

Fonoster is researching an innovative Programmable Telecommunications Stack that will allow businesses to connect telephony services with the Internet entirely through a cloud-based utility.

  • Multitenancy
  • Easy deployment of PBX functionalities
  • Programmable Voice Applications
  • NodeJS SDK
  • Support for Amazon Simple Storage Service (S3)
  • Secure API endpoints with Let's Encrypt

Getting it running

Setup follows the usual MCP pattern — install or clone the server, register it in your client's configuration file, restart the client.

The tools it exposes

The server publishes 12 tools. What each one is for:

  • Answer — Accepts an incoming call
  • Hangup — Closes the call
  • Play — Takes a URL with a media file and streams the sound back to the calling party
  • PlayDtmf — Takes a DTMF sequence and plays it back to the calling party
  • Say — Takes a text, synthesizes the text into audio, and streams back the result
  • Gather — Waits for DTMF or speech events and returns back the result
  • SGather — Returns a stream for future DTMF and speech results
  • Stream — Creates a bidirectional stream to send and receive audio from a caller
  • Dial — Passes the call to an Agent or a Number at the PSTN
  • Record — It records the voice of the calling party and saves the audio on the Storage sub-system
  • Mute — It tells the channel to stop sending media, effectively muting the channel
  • Unmute — It tells the channel to allow media flow

Things to watch

  • It runs with your machine's permissions. That is convenient and also the reason to think about what you point it at before you approve a tool call.
  • With 12 tools registered it takes up a noticeable share of the context window; turn it off in projects that never touch Fonoster.
  • Keep per-call confirmation enabled while you learn its behaviour; it is the cheapest safeguard you have.

How it compares

This sits in the AI and media services group, where several servers overlap in what they claim to do but differ sharply once you actually set them up. Fonoster's toolset — Answer, Hangup, Play and 9 more — is a fair guide to whether it matches your workflow. It is maintained by fonoster; worth a glance at recent repository activity before you build anything load-bearing on it.

We check each listing at SyncDev against the project's documentation before it goes live — if something here drifts out of date, it is a bug worth reporting.

Available tools

ToolWhat it does
AnswerAccepts an incoming call
HangupCloses the call
PlayTakes a URL with a media file and streams the sound back to the calling party
PlayDtmfTakes a DTMF sequence and plays it back to the calling party
SayTakes a text, synthesizes the text into audio, and streams back the result
GatherWaits for DTMF or speech events and returns back the result
SGatherReturns a stream for future DTMF and speech results
StreamCreates a bidirectional stream to send and receive audio from a caller
DialPasses the call to an Agent or a Number at the PSTN
RecordIt records the voice of the calling party and saves the audio on the Storage sub-system
MuteIt tells the channel to stop sending media, effectively muting the channel
UnmuteIt tells the channel to allow media flow

Example prompts to try

  • Use Fonoster to Answer.
  • Use Fonoster to Hangup.
  • Use Fonoster to Play.

Frequently asked questions

Fonoster offers features such as multitenancy, programmable voice applications, a NodeJS SDK, secure API endpoints with Let's Encrypt, and Role-Based Access Control (RBAC). It also integrates with technologies like Kubernetes and supports Google Speech APIs.