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A minimal support agent: when an email arrives, an LLM drafts a reply and Sentvia sends it back in the same thread. The pattern is webhook → generate → reply.

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1. Register a webhook

curl -X POST https://api.sentvia.ai/v1/webhooks \
  -H "Authorization: Bearer sv_live_…" -H "Content-Type: application/json" \
  -d '{ "url": "https://your-app.com/sentvia", "events": ["message.received"] }'
Store the returned signing secret.

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2. Handle inbound and reply

import crypto from "node:crypto";

const KEY = process.env.SENTVIA_KEY!;
const SECRET = process.env.SENTVIA_WEBHOOK_SECRET!;
const API = "https://api.sentvia.ai/v1";

// Express-style handler. Use the RAW body for signature verification.
export async function handler(req, res) {
  const sig = req.headers["x-sentvia-signature"];
  const expected = "sha256=" + crypto.createHmac("sha256", SECRET).update(req.rawBody).digest("hex");
  if (sig !== expected) return res.status(401).end();

  const { event, message } = JSON.parse(req.rawBody);
  if (event !== "message.received") return res.status(200).end();

  // 1. draft a reply with your LLM of choice
  const reply = await draftReply(message.subject, message.body_text);

  // 2. send it in-thread
  await fetch(`${API}/messages/${message.id}/reply`, {
    method: "POST",
    headers: { Authorization: `Bearer ${KEY}`, "Content-Type": "application/json" },
    body: JSON.stringify({ text: reply }),
  });

  res.status(200).end();   // respond fast; do heavy work async
}
Replies thread automatically — Sentvia sets In-Reply-To/References and prefixes the subject with Re:. No need to track headers yourself.

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Going further

  • Add a block list rule so the agent ignores known spammers.
  • Use the realtime WebSocket instead of (or alongside) webhooks for a live view.
  • Want native tools instead of REST? Connect via MCP.