@cellar-door/mcp-server

@cellar-door/mcp-server

⚠️ Pre-release software — no formal security audit has been conducted. This project is published for transparency, review, and community feedback. It should not be used in production systems where security guarantees are required. If you find a vulnerability, please report it to [e-mail].

MCP (Model Context Protocol) server that exposes cellar-door-exit and cellar-door-entry verifiable markers as AI-native tools. Any MCP-compatible client — Claude Desktop, Cursor, Windsurf, or custom agents — can create, sign, and verify EXIT and ENTRY markers.

Tools

EXIT Tools

Tool	Description
generate_identity	Generate an Ed25519 DID keypair for signing
quick_exit	One-shot: create + sign a departure marker
create_exit_marker	Create and sign a marker with full options
verify_exit_marker	Verify a marker from JSON

ENTRY Tools

Tool	Description
verify_and_admit	Verify EXIT marker, evaluate admission policy, create arrival
evaluate_admission	Check if EXIT marker meets an admission policy
verify_transfer	Verify a complete EXIT→ENTRY transfer chain
list_admission_policies	List available admission policy presets

Quick Start

npm install @cellar-door/mcp-server

Claude Desktop

{
  "mcpServers": {
    "cellar-door": {
      "command": "npx",
      "args": ["@cellar-door/mcp-server"],
      "env": {
        "CELLAR_DOOR_SERVER_POLICY": "STRICT"
      }
    }
  }
}

⚠️ Security: Admission Policy

IMPORTANT: By default, the server uses STRICT admission policy when no policy is specified by the LLM. This is intentional — an LLM can freely choose the most permissive policy (OPEN_DOOR) or omit the parameter entirely to bypass admission checks.

For production deployments, always set a server-side policy override using one of:

• Environment variable: CELLAR_DOOR_SERVER_POLICY=STRICT (or EMERGENCY_ONLY)
• Constructor option: createServer({ serverPolicy: "STRICT" })

When serverPolicy is set, any LLM-provided admissionPolicy parameter is ignored.

Available policies: OPEN_DOOR, STRICT, EMERGENCY_ONLY.

CELLAR_DOOR_SERVER_POLICY

Value	Behavior
OPEN_DOOR	Accept any departure with a valid signature
STRICT	Voluntary only, <24h old, requires lineage + stateSnapshot modules
EMERGENCY_ONLY	Accept only emergency exits

Sample Conversation (Claude Desktop)

Below is an example of how the tools work in a conversation with Claude Desktop:

User: I need to leave Platform X. Can you create a departure record?

Claude: I'll create a signed EXIT marker for your departure from Platform X.

→ Calls: quick_exit({ origin: "did:web:platform-x.example.com", reason: "Migrating to new platform" })

Claude: Here's your signed departure marker:
- ID: exit:abc123...
- Subject: did:key:z6Mk...
- Origin: did:web:platform-x.example.com
- Exit Type: Voluntary
- Signature: ✅ Verified

The marker has been cryptographically signed. You can share this JSON with
your destination platform to prove your voluntary departure.

User: Now verify this on Platform Y and create my arrival.

→ Calls: verify_and_admit({
    exitMarkerJson: "{...the exit marker JSON...}",
    destination: "did:web:platform-y.example.com",
    admissionPolicy: "STRICT"
  })

Claude: Admission result:
- ✅ Admitted
- Arrival marker created with ID: urn:entry:def456...
- Continuity verified between EXIT and ENTRY markers

User: Can you verify the complete transfer?

→ Calls: verify_transfer({
    exitMarkerJson: "{...exit marker...}",
    arrivalMarkerJson: "{...arrival marker...}"
  })

Claude: Transfer verification:
- ✅ Both signatures valid
- ✅ Subject continuity maintained
- ✅ Temporal ordering correct
- Transfer time: 2.3 seconds

Programmatic Usage

import { createServer } from "@cellar-door/mcp-server";

const server = createServer({
  // Lock admission policy server-side (recommended for production)
  serverPolicy: "STRICT",
});

Example Tool Calls

Quick Exit

{
  "name": "quick_exit",
  "arguments": { "origin": "did:example:my-agent", "reason": "Task complete" }
}

Verify and Admit

{
  "name": "verify_and_admit",
  "arguments": {
    "exitMarkerJson": "{...exit marker JSON...}",
    "destination": "did:example:new-platform",
    "admissionPolicy": "OPEN_DOOR"
  }
}

Response:

{
  "admitted": true,
  "arrivalMarker": { "..." },
  "exitMarkerId": "exit:...",
  "continuity": { "valid": true, "errors": [] }
}

Verify Transfer

{
  "name": "verify_transfer",
  "arguments": {
    "exitMarkerJson": "{...exit marker...}",
    "arrivalMarkerJson": "{...arrival marker...}"
  }
}

Response:

{
  "verified": true,
  "transferTime": 1234,
  "errors": [],
  "continuity": { "valid": true, "errors": [] }
}

Evaluate Admission

{
  "name": "evaluate_admission",
  "arguments": {
    "exitMarkerJson": "{...}",
    "policy": "STRICT"
  }
}

List Admission Policies

{ "name": "list_admission_policies", "arguments": {} }

Response:

{
  "policies": {
    "OPEN_DOOR": { "description": "Accept everything with a valid signature", "requireVerifiedDeparture": true },
    "STRICT": { "description": "Voluntary only, <24h old, requires lineage + stateSnapshot", "..." },
    "EMERGENCY_ONLY": { "description": "Accept only emergency exits", "..." }
  }
}

⚠️ Disclaimer

WARNING: Automated admission decisions should be reviewed by platform operators. This integration does not constitute legal advice. Platforms are responsible for their own admission policies and the consequences of admitting agents.

License

Apache-2.0