A curated list of tools, platforms, and SDKs for connecting AI agents to the world — phone calls, SMS, messaging apps, and beyond.
50+ tools across 7 categories. Everything you need to give your AI agent a voice, a phone number, or a presence on messaging platforms.
- Telephony & Voice APIs — Phone numbers, voice calls, SMS
- Voice Agent Platforms — Turnkey voice AI infrastructure
- Messaging Platforms — WhatsApp, Telegram, Discord, Slack
- Multi-Channel Agent Hubs — One agent, every platform
- Open-Source Voice & Audio — STT, TTS, conversation
- Protocols & Standards — MCP, A2A, agent-to-agent
- Learning Resources
Give your AI agent a real phone number. Programmable voice, SMS, and calling infrastructure.
| Tool | Description | Pricing |
|---|---|---|
| AgentLine | Open-source telephony API purpose-built for AI agents. Phone numbers, voice calls, SMS, MCP server, LangChain integration, skill-based install. Works with OpenClaw, Hermes, Claude Code, and any LLM. | $2/number, $0.10/min |
| Twilio | General-purpose cloud communications platform. Voice, SMS, video, WhatsApp API. Requires managing WebSocket streams for AI integration. | Pay-as-you-go |
| SignalWire | Twilio-compatible API with open-source core. AI agent support via SWAIG and Relay. | Pay-as-you-go |
| Vonage | Voice, SMS, video APIs. Nexmo heritage. AI studio for building conversational agents. | Pay-as-you-go |
| Telnyx | Carrier-grade voice and SMS. AI call control, real-time transcription APIs. | Pay-as-you-go |
| Plivo | Cloud API platform for voice and SMS. Simple pricing, global coverage. | Pay-as-you-go |
Turnkey infrastructure for building voice-enabled AI agents. Sub-300ms latency, natural conversation.
| Platform | Description | Pricing |
|---|---|---|
| Vapi | Developer-first voice AI. Low-latency, model-agnostic. Handles STT, TTS, and conversation flow. | Usage-based |
| Bland AI | Outbound call automation platform. CRM integration, SOC2/HIPAA compliant. | Usage-based |
| Retell AI | Human-like voice agents. Multi-language, telephony integration built-in. | Usage-based |
| ElevenLabs | Industry benchmark for voice AI. Conv AI 2.0 — RAG, multimodal, batch calling. 75ms latency. HIPAA. | Free / $5+/mo |
| Synthflow | No-code voice agents for SMBs. Pre-built templates, easy deployment. | From $29/mo |
| Voiceflow | No-code voice and chat builder. Drag-and-drop conversation design. | Free / $50+/mo |
| PolyAI | Enterprise voice agents. Natural multi-turn conversation. Hospitality and retail focus. | Enterprise |
| HeyGen | AI avatars with voice. Real-time interactive streaming. | From $24/mo |
| Deepgram | STT and TTS APIs. Sub-300ms latency. Nova-3 model for real-time. | Usage-based |
| AssemblyAI | STT with diarization, sentiment analysis, entity detection, summarization. | Usage-based |
Connect your AI agent to messaging apps where users already are.
| Platform | Description | Pricing |
|---|---|---|
| WhatsApp Cloud API | Meta's official API. Send/receive messages, templates, media. Free tier available. | Free / Pay-per-conversation |
| Telegram Bot API | Free, feature-rich bot API. Inline queries, keyboards, payments, webhooks. | Free |
| Discord API | Bot and webhook APIs. Slash commands, message components, voice channels. | Free |
| Slack API | Bot users, slash commands, interactive messages. Block Kit for rich UIs. | Free |
| Signal | End-to-end encrypted messaging. Signal-CLI for automation. | Free |
| Facebook Messenger | Bot API for Messenger. Templates, quick replies, persistent menus. | Free |
| iMessage (Messages API) | Apple Messages for Business. Rich links, interactive messages. | Apple Developer |
| Matrix | Open federated protocol. Bridges to other platforms. Element clients. | Free (self-hosted) |
One agent, every platform. Deploy once, reach users everywhere.
| Platform | Description | Pricing |
|---|---|---|
| OpenClaw | Self-hosted agent runtime across WhatsApp, Telegram, Slack, Discord, Signal. 5,700+ community skills. 188k GitHub stars. | Free (OSS) |
| Hermes Agent | Nous Research's agent with native WhatsApp, Telegram, and webhook connectivity. Persistent memory, skills system, cron scheduler. | Free (OSS) |
| Meta AI | Llama-powered AI built into WhatsApp, Messenger, and Instagram. Native platform integration. | Free |
| Coze | ByteDance's agent builder. Deploy to Telegram, Discord, Slack, web widgets. Visual workflow builder. | Free / Paid |
| Botpress | Open-source conversational AI platform. Deploy to WhatsApp, Telegram, Messenger, web. Visual flow builder. | Free / Cloud |
| Rasa | OSS conversational AI framework. NLU-based. Deploy anywhere. Enterprise CALM add-on for generative. | Free (OSS) |
Build your own voice pipeline. STT, TTS, conversation orchestration.
| Tool | Description |
|---|---|
| LiveKit Agents | OSS framework for real-time voice/video AI agents. Python and TypeScript. |
| Pipecat | OSS framework for voice and multimodal conversational AI. Python. |
| Vocode | OSS library for building voice-based LLM agents. Handles STT → LLM → TTS pipeline. |
| Whisper | OpenAI's open-source speech recognition. Multilingual, robust. |
| Coqui TTS | Open-source text-to-speech. 100+ languages, voice cloning. |
| Piper | Fast, local neural TTS. Runs on Raspberry Pi. 100+ voices. |
| Faster Whisper | CTranslate2-based Whisper. 4x faster, lower memory. |
| OpenVoice | Instant voice cloning. Granular control over tone, emotion, accent. |
Standards for agent communication and interoperability.
| Standard | Description |
|---|---|
| MCP (Model Context Protocol) | Anthropic's open protocol for AI-tool integration. Server/client architecture. |
| A2A (Agent-to-Agent) | Google's open protocol for agent-to-agent communication and task delegation. |
| Agent Protocol | Standard API interface for AI agents. Interoperability across frameworks. |
| AGNTCY | Cisco-led open-source project for agentic workflow orchestration. |
| WhatsApp Cloud API | De facto messaging standard. Used by most multi-channel AI platforms. |
- AgentLine Blog — Tutorials on giving AI agents phone numbers
- OpenClaw Documentation — Multi-platform agent deployment
- Hermes Agent Docs — WhatsApp/Telegram connectivity
- Vapi Documentation — Voice AI development guides
- ElevenLabs Docs — Conversational AI guides
- Telegram Bot API Docs — Build bots for Telegram
- WhatsApp Cloud API Docs — Official Meta docs
- Discord Developer Portal — Build Discord bots
Contributions welcome! Please see the contribution guidelines.
Add tools by submitting a PR — keep entries alphabetical within each category. Include the tool name, link, brief description, and pricing model.
To the extent possible under law, the maintainers have waived all copyright and related rights to this work.