vault_store · Mailgent MCP Server MCP: Risk & Policy

WHAT IT DOES

What vault_store does on Mailgent MCP Server

AI agents use vault_store 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_store needs a policy

This tool creates or modifies encrypted credentials reversibly in a vault system. While it handles sensitive information (API keys, cards, addresses), the action itself is a Write operation—storing/updating data that can theoretically be replaced or removed.

From the tool's definition Tool description explicitly states 'Store or update an encrypted credential in the vault', indicating creation and modification of sensitive data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

vault_store Rate-limited

vault_store 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_store": {
      "limits": [
        {
          "counter": "vault_store_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

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_store

What does the vault_store tool do? +

Store or update an encrypted credential in the vault. Prefer the typed helpers (vault_storeApiKey, vault_storeCard, vault_storeShippingAddress) when they fit. 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_store? +

Register the Mailgent MCP Server MCP server in PolicyLayer and add a rule for vault_store: 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_store? +

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

Can I rate-limit vault_store? +

Yes. Add a rate_limit block to the vault_store 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_store completely? +

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

vault_store 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.