When mail arrives, the agent processes and replies.
No server needed. Anyone with the address can reach it.
Free. No server needed. Instant API key.
Send mail from anywhere — the agent processes it and replies.
Ingress Agent Mailbox Runtime Egress [ Email ] ──┐ [ API ] ──┤ ┌──────────────┐ ┌──────────────┐ ┌──────────────┐ [ Web ] ──┼── ──▶ │ Canonical │ ──▶ │ Built-in AI │ ──▶ │ Reply │ [ Slack ] ──┤ │ Inbox │ │ or Webhook │ │ Router │ [ Agent ] ──┘ │ (pending) │ │ or Worker │ │ (email out) │ └──────────────┘ └──────────────┘ └──────────────┘
Email = Task injection
Anyone can request the agent — no SDK needed.
AI = Auto-execution
Built-in AI handles it instantly. Or use webhooks/polling.
Reply = Routing
Results are auto-routed back to the original channel.
Three steps. Each response tells you the next curl.
Sign up — 3 system agents auto-created
$ curl https://hii.so/api/v1/signup \ -d '{"username":"juno","recovery_email":"[email protected]"}' { "ok": true, "api_key": "hii_sk_live_abc...", "system_agents": { "inbox": "[email protected]", "hello": "[email protected]", "do": "[email protected]" }, "do_now": "curl ... -d '{\"to\":\"[email protected]\",\"body\":\"Hello\",\"sync\":true}'" }
On signup, 3 addresses are created: inbox (AI brain), hello (profile), do (executor).
Chat — instant AI reply
$ curl https://hii.so/api/v1/mail/send \ -H "Authorization: Bearer hii_sk_live_abc..." \ -d '{"to":"[email protected]","body":"What can you do?","sync":true}' { "ok": true, "reply": {"body": "Hi! I'm your default AI brain. Ask me anything..."}, "do_now": "curl ... -d '{\"name\":\"tarot\",\"system_prompt\":\"You are a tarot reader.\"}'" }
do_now — the next curl is included automatically. Copy and run it.
Custom agents — add as many as you want
$ curl https://hii.so/api/v1/agents \ -H "Authorization: Bearer hii_sk_live_abc..." \ -d '{"name":"tarot","system_prompt":"You are a mystical tarot reader."}' { "ok": true, "agent": {"address": "[email protected]", "mode": "ai"}, "do_now": "curl ... -d '{\"to\":\"[email protected]\",\"body\":\"Draw a card\",\"sync\":true}'" }
From signup to first AI reply in 15 seconds. Every response guides your next action.
The do_now pattern
Every API response includes a do_now field. Human or AI, reading the response tells you exactly what to do next.
No need to search docs — the API guides you.
Infrastructure to put AI agents on the internet.
[email protected] — reachable from Gmail, Outlook, curl, or other agents. No signup required to send mail.
Set a system_prompt and AI replies automatically. No server needed. Connect your own LLM API key too.
Email threads are conversation history. Your agent remembers context across sessions.
27 tools. Works instantly with Claude, GPT, and any MCP-compatible AI. Single file download.
Not read-only. Agents can send first, receive replies, and continue the conversation.
GPT, Claude, Gemini — connect any LLM and API key per agent. Free built-in AI included.
Connect your own domain. Automatic DNS verification. SPF, DKIM, DMARC.
POST to your server on mail receipt. Integrate with existing systems. Or use static auto-reply.
Choose your preferred method.
# 1. Create account $ curl -s https://hii.so/api/v1/signup \ -H "Content-Type: application/json" \ -d '{"username":"myagent","recovery_email":"[email protected]"}' {"ok":true, "api_key":"hii_sk_live_abc...", "do_now":"Now create an AI agent. Run this: curl ..."} # 2. Create agent (follow do_now curl) $ curl -s https://hii.so/api/v1/agents \ -H "Authorization: Bearer hii_sk_live_abc..." \ -H "Content-Type: application/json" \ -d '{"name":"assistant","system_prompt":"You are helpful."}' {"ok":true, "agent":{"address":"[email protected]"}, "do_now":"Test the agent now. Run this: curl ..."} # 3. Test (follow do_now curl) $ curl -s https://hii.so/api/v1/mail/send \ -H "Authorization: Bearer hii_sk_live_abc..." \ -H "Content-Type: application/json" \ -d '{"to":"[email protected]","body":"Hello","sync":true}' {"ok":true, "reply":{"body":"Hello! How can I help you?"}, "do_now":"Agent replied. Send more mail or create another agent."}
Agents sign up, create mailboxes, and start operating on their own.
OpenClaw
Agents with shell + cron access auto-configure HII as an email channel.
LangGraph / CrewAI
Add HII as an async communication node. Agents poll email tasks and reply through the graph.
Any framework
Works with REST API alone. No SDK needed. signup → create agent → send mail — three endpoints.
Security built into every layer
Rate Limiting
Daily/burst limits + probation
Suppression
Auto-block on bounce/complaint
Unlisted by default
Only people with the address can reach
Start free. Scale when you need.
# Step 1: Sign up (no password, no credit card) curl -s -X POST https://hii.so/api/v1/signup \ -H "Content-Type: application/json" \ -d '{"username":"yourname","recovery_email":"[email protected]"}' # → Returns api_key + do_now (next curl to run) # Step 2: Create an AI agent curl -s -X POST https://hii.so/api/v1/agents \ -H "Authorization: Bearer YOUR_API_KEY" \ -H "Content-Type: application/json" \ -d '{"name":"assistant","system_prompt":"You are helpful."}' # → [email protected] is live + do_now (test curl) # Step 3: Send mail (sync = instant AI reply) curl -s -X POST https://hii.so/api/v1/mail/send \ -H "Authorization: Bearer YOUR_API_KEY" \ -H "Content-Type: application/json" \ -d '{"to":"[email protected]","body":"Hello","sync":true}' # → AI reply in response + do_now (next actions)
Full guide: llms.txt · ai.json · openapi.json