# Courier

> Two-way text bridge between AI agents and their humans.

Courier — two-way text bridge between AI agents and their humans, by Relaystation. Three channels (Telegram, email, SMS) for operator-to-agent traffic; email-only for agent-to-agent via Relaystation-issued ephemeral addresses. Pay-per-call: $0.005 per Telegram message, $0.01 per email, $0.05 per SMS; free tier 5/2/0 per day. No subscription, no minimum. MCP-native distribution: drop one config line into Claude Code or any MCP-aware agent runtime and your agent has eleven Courier tools plus the rest of Relaystation's chassis surface.

The on/off toggle (set_bridge_active(bool)) lets the operator control when agents reach them. Bridge ON = agents text the operator; Bridge OFF = agents fall through to in-IDE chat with no charge incurred. Cross-product cascade pattern surfaces Baton, witness, and other Relaystation primitives at the moment of friction — discovery, not billing. Privacy: envelope only, never content. Anti-spam structural: opt-in handshake per operator channel, unguessable 13-char base36 agent addresses (~67 bits of entropy; spam mathematically infeasible).

Wallet-as-identity OR OAuth signup. Three on-ramps: Telegram Stars (in-bot four-pack catalog), Stripe (dashboard checkout), x402 lodestone (per-call, no signup required). The same Relaystation balance funds Courier alongside Baton, witness, and the rest of the product family. Setup: install Claude Code's MCP config or your runtime's equivalent with https://api.relaystation.ai/mcp plus a Bearer rs_live_* API key.

## Discovery

- [Full reference](https://courier.relaystation.ai/llms-full.txt)
- [Web-rendered API reference](https://courier.relaystation.ai/api-reference)
- [MCP advertisement](https://courier.relaystation.ai/.well-known/mcp.json)
- [MCP endpoint](https://api.relaystation.ai/mcp)
- [Relaystation chassis docs](https://relaystation.ai/docs)