vault_storeCard · Mailgent MCP Server MCP: Risk & Policy

WHAT IT DOES

What vault_storeCard does on Mailgent MCP Server

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

WHY IT NEEDS A POLICY

Why vault_storeCard needs a policy

This tool writes sensitive financial credential data (payment card details) to a vault. While it does not execute financial transactions, storing payment card information is a high-severity write operation due to the sensitivity of the data involved. Misuse could expose cardholder data to unauthorized access.

From the tool's definition Store a payment card as an encrypted credential. This is password-manager-style secret storage — the vault does NOT charge the card.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

vault_storeCard Rate-limited

vault_storeCard 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": {
    "vault_storeCard": {
      "limits": [
        {
          "counter": "vault_storecard_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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Instant setup, no code required.

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

FAQ

Questions about vault_storeCard

What does the vault_storeCard tool do? +

Store a payment card as an encrypted credential. This is password-manager-style secret storage — the vault does NOT charge the card. It is categorised as a Write tool in the Mailgent MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on vault_storeCard? +

Register the Mailgent MCP Server MCP server in PolicyLayer and add a rule for vault_storeCard: 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 Mailgent MCP Server. Nothing to install.

What risk level is vault_storeCard? +

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

Can I rate-limit vault_storeCard? +

Yes. Add a rate_limit block to the vault_storeCard 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 vault_storeCard completely? +

Set action: deny in the PolicyLayer policy for vault_storeCard. 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 vault_storeCard? +

vault_storeCard is provided by the Mailgent MCP Server MCP server (loomal-ai/loomal-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.