bottle_send · Cartridge MCP: Risk & Policy

WHAT IT DOES

What bottle_send does on Cartridge

AI agents use bottle_send to create or update resources in Cartridge — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Cartridge environment.

WHY IT NEEDS A POLICY

Why bottle_send needs a policy

This is a Write operation because it creates and sends a message to another vessel, which modifies state in the recipient system. It is not Read (no query), Execute (no code/command execution), Destructive (reversible), Financial (no money involved), or Other.

From the tool's definition Tool name 'bottle_send' and description 'Send a message-in-a-bottle to another vessel' indicate the tool creates and transmits a message artifact to another system/entity.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

bottle_send Rate-limited

bottle_send stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "bottle_send": {
      "limits": [
        {
          "counter": "bottle_send_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Cartridge, so you can run agents against it safely.

FAQ

Questions about bottle_send

What does the bottle_send tool do? +

Send a message-in-a-bottle to another vessel. It is categorised as a Write tool in the Cartridge MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on bottle_send? +

Register the Cartridge MCP server in PolicyLayer and add a rule for bottle_send: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Cartridge. Nothing to install.

What risk level is bottle_send? +

bottle_send is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit bottle_send? +

Yes. Add a rate_limit block to the bottle_send rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block bottle_send completely? +

Set action: deny in the PolicyLayer policy for bottle_send. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides bottle_send? +

bottle_send is provided by the Cartridge MCP server (lucineer/cartridge-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.