SignalWire

Overview

SignalWire is a programmable communications platform built by the team behind FreeSWITCH. It covers voice, SMS, MMS, WhatsApp, video, fax and in-app chat, and its main pitch is AI agents defined in code that run inside its media engine. The same agent can answer phone calls and hold text conversations over SMS, and a Compatibility API accepts Twilio-style requests.

Key features

• Messaging API for SMS, MMS and WhatsApp, with 10DLC registration by API
• Agents SDK with tool calling, multi-step contexts, skills and knowledge search, in Python, TypeScript and other languages
• AI agents that move a conversation between text and a phone call
• Programmable voice over PSTN, SIP and WebRTC, plus a visual Call Flow Builder
• HMAC-signed webhooks and a message logs API
• Local agent testing with the swaig-test CLI
• LiveKit-compatible LiveWire layer and ElevenLabs agents over SIP
• SOC 2 Type II, ISO 27001, GDPR, PCI and HIPAA BAAs, with a 99.95% uptime SLA

Pricing

Pay as you go. US 10DLC SMS costs $0.00415 per segment in each direction, MMS $0.02 outbound, WhatsApp $0.005 per message plus Meta fees, and the AI agent runtime $0.16 a minute. Local numbers cost $0.50 a month and toll-free numbers $0.80; porting in is free. New accounts start in trial mode until at least $5 of credit is added.

How it compares to Linq

SignalWire does not offer iMessage or RCS. Linq sends iMessage, RCS and SMS from one API at a flat monthly price from $260 with no per-message fees; SignalWire bills per segment and per minute. SignalWire places and answers calls and runs voice AI agents, while Linq's docs say its API does not place or answer calls. Both report SOC 2 Type II and sign webhooks with HMAC.

Best for

Teams building voice-first AI agents that also need SMS or WhatsApp on the same number.

Sources

• signalwire.com/llms.txt
• signalwire.com/docs/llms.txt
• signalwire.com/docs/server-sdks/llms.txt
• signalwire.com/docs/apis/llms.txt
• signalwire.com/pricing
• signalwire.com/segment/enterprise
• signalwire.com/docs/platform/messaging
• signalwire.com/docs/platform/messaging/whatsapp
• signalwire.com/docs/platform/ai/chat
• signalwire.com/docs/platform/webhooks
• signalwire.com/docs/server-sdks
• signalwire.com/docs/server-sdks/guides/testing
• signalwire.com/docs/server-sdks/guides/mcp-gateway
• signalwire.com/docs/server-sdks/reference/python/agents/cli
• signalwire.com/docs/server-sdks/reference/python/agents/livewire
• signalwire.com/docs/apis/rest/message-logs/list-message-logs
• signalwire.com/docs/platform/signing-up-for-a-space
• signalwire.com/use-case/contact-center
• github.com/signalwire