Skip to content

Briefflink – Briefe mit KI versenden

by briefflink.de · remote · no sign-in to list tools · v1.0.0 · published by de.briefflink

Send real paper letters from AI chat: print, envelope, postage, delivery. Pay per letter.

Final · 1Changes · 1
CompareRegistry entry

4 tools: 1 do something that can't be undone, 1 change things and 2 only read.

Scanned Oct 21, 2026

No check matched anything in the tool definitions. No finding is not a safety guarantee. How the checks work.

claude mcp add --transport http letter https://briefflink.de/api/mcp.php

Tools

Open a tool for its reasons and full description. Descriptions are the publisher's own words, shown as they are.

4 tools

Can't be undone 1Claude Code: ask
  • send_letterLegt einen Briefauftrag an und gibt einen Stripe-Bezahllink zurück.Reads text others writeCan send data outNo findings

    Why it is in this group

    • The name "send_letter" says "send": a word for sending, and what is sent cannot be taken back.

    What it can reach

    • untrusted-inputThe server marks it openWorldHint: true: it reaches things outside the server's own data.
    • outboundThe name "send_letter" says "send": it sends or publishes something to other people.
    Description, as the server wrote it
    Legt einen Briefauftrag an und gibt einen Stripe-Bezahllink zurück. Der Brief wird erst gedruckt und versendet, wenn der Nutzer bezahlt hat. Dokument per upload_id (aus create_upload_link) oder pdf_base64.

    Annotations the server declares

    • readOnlyHint: false
    • destructiveHint: false
    • openWorldHint: true
Changes things 1Claude Code: ask
Only reads 2Claude Code: allow
  • get_letter_priceBerechnet den Endpreis eines Briefes (Druck, Kuvert, Porto) aus Seitenzahl, Einschreiben-Wahl und Zielland.No findings

    Why it is in this group

    • The name "get_letter_price" says "get": a word for reading.
    Description, as the server wrote it
    Berechnet den Endpreis eines Briefes (Druck, Kuvert, Porto) aus Seitenzahl, Einschreiben-Wahl und Zielland. Kein Auftrag, keine Kosten.

    Annotations the server declares

    • readOnlyHint: true
    • openWorldHint: false
  • get_letter_statusZeigt, ob ein Auftrag noch auf Zahlung wartet, bezahlt, versendet oder fehlgeschlagen ist.No findings

    Why it is in this group

    • The name "get_letter_status" says "get": a word for reading.
    Description, as the server wrote it
    Zeigt, ob ein Auftrag noch auf Zahlung wartet, bezahlt, versendet oder fehlgeschlagen ist.

    Annotations the server declares

    • readOnlyHint: true
    • openWorldHint: false

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Exfil surface

Which tools read private data, which read text someone else can write, and which can send data out. One of each is a path a prompt injection can use.

No private-data, untrusted-input, outbound path in this server alone: no tool is tagged private-data.

Reads private data0
Reads files, mail, messages, databases, secrets, calendars or repositories.
Reads text others write1
Brings in text someone else can write: web pages, inbound email, messages, issues and comments.
Can send data out1
Can carry data to people or systems: it sends, posts or publishes, or takes a recipient, channel or URL.

Other servers in the same agent add their own tools to these paths. Audit your whole setup to see them together.

Remote posture

What anyone on the internet sees at the remote endpoint: an anonymous initialize and tools/list, and the public OAuth metadata.

Looked at Oct 22, 2026, 14:45 UTC, unchanged since Oct 22, 2026. No credentials were sent and no tool was called. What is looked at.

Reachable
yes
HTTP status of an anonymous initialize
200
tools/list served without credentials
yes
Tools that change things, listed without credentials
2
Protocol version
2025-06-18
WWW-Authenticate on 401
not observed
resource_metadata in WWW-Authenticate
none
RFC 9728 protected resource metadata
none
Authorization servers
none
Legacy HTTP+SSE transport
no
Dynamic client registration
not observed
Client ID metadata documents
not observed
  • HighThe whole server

    The endpoint served tools/list without credentials, and the list has 2 tools that change things (1 irreversible, 1 write). Whether a call also works without credentials was not tested: tools are never called.

    Matched text

    https://briefflink.de/api/mcp.php: tools/list returned 4 tools to an anonymous client, including send_letter (irreversible), create_upload_link (write)

    What this check looks for

Install

Pinned to version 1.0.0. Values in angle brackets are yours to fill in.

claude mcp add --transport http letter https://briefflink.de/api/mcp.php

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change or a way out, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json
{
  "permissions": {
    "allow": [
      "mcp__letter__get_letter_price",
      "mcp__letter__get_letter_status"
    ],
    "ask": [
      "mcp__letter__create_upload_link",
      "mcp__letter__send_letter"
    ],
    "deny": []
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. A read that can send data out (it takes a URL, say) asks first too. It assumes the server is installed as letter. Review it before you use it.

Capability tags behind 1 rule
  • mcp__letter__send_letter untrusted-input, outbound