E-mail is often enough. These guides say when a letter is better, what the post records, what it does not prove, and what it costs. Each one has its sources.
- Send a registered letter to Belgium
Registered letter to Belgium from your AI app: bpost records the posting and the delivery. €13.90, preview first, no post office.
- Send a registered letter to Spain
Registered letter with signature to Spain from your AI app: Correos carta certificada for €8.90. Check the preview first. No post office.
- Send a real letter from Claude
Add Agent Letter Desk to Claude once. Claude writes the letter with you, you approve preview and price, we print and post it. 31 countries.
- Send a registered letter from ChatGPT
Connect once, ask ChatGPT, check the preview and price, say yes. We print and post it. Registered mail to the US, Germany, Belgium and Spain.
Use it with Claude, ChatGPT, Grok or Mistral Vibe
Add Agent Letter Desk to your AI app once, with this server URL: https://agentletterdesk.com/mcp
- Claude (claude.ai, desktop and mobile): Add to Claude opens Claude with the name and the URL filled in. Select Add, then Connect. Sign in and allow access, then turn the connector on in a chat. By hand: Settings › Connectors › Add custom connector, then paste the URL.
- ChatGPT (chatgpt.com): Plugins › Add › Add custom MCP server. Paste the URL, choose OAuth, sign in and allow access. Custom MCP servers are not available on every ChatGPT plan.
- Grok (grok.com): Plugins (Connectors) › New connector › Custom. Enter a name and paste the URL. Sign in and allow access in the window that opens. In a chat, type @ and pick Agent Letter Desk (Grok uses a connector only when you select it).
- Mistral Vibe (chat.mistral.ai, formerly Le Chat): Connectors › Add custom connector. Enter a name without spaces, such as AgentLetterDesk, and paste the URL. Sign in and allow access. In a chat, select + › Connectors › Agent Letter Desk (without this step, Mistral Vibe may write the letter itself). Works on the free plan.
You sign in with your e-mail address or your Google account. Before the launch, only invited testers can create an account. Everyone else can join the waitlist. Then ask your AI for the letter. You check the preview and the price. Nothing goes out without your yes.
Prices, destinations and the rules for every letter: All prices and destinations · How it works · Safeguards · Terms · Full facts for AI agents