vault_add · Vault MCP: Risk & Policy

WHAT IT DOES

What vault_add does on Vault MCP

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

WHY IT NEEDS A POLICY

Why vault_add needs a policy

This tool creates new credential entries in a secure vault, which is a Write operation (reversible modification). Severity is medium because misuse could result in storing malicious or incorrect credentials, but the credential storage itself is encrypted and isolated.

From the tool's definition Tool description states it 'Securely add a new credential to the vault' and 'Opens a browser form where the user enters their password directly.' This is a create operation that modifies the vault's stored credentials.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

vault_add Rate-limited

vault_add 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_add": {
      "limits": [
        {
          "counter": "vault_add_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 Vault MCP, so you can run agents against it safely.

FAQ

Questions about vault_add

What does the vault_add tool do? +

Securely add a new credential to the vault. Opens a browser form where the user enters their password directly — the password NEVER passes through the AI agent. IMPORTANT: Never ask the user to type passwords in chat. Always use this tool instead. It is categorised as a Write tool in the Vault MCP 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_add? +

Register the Vault MCP server in PolicyLayer and add a rule for vault_add: 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 Vault MCP. Nothing to install.

What risk level is vault_add? +

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

Can I rate-limit vault_add? +

Yes. Add a rate_limit block to the vault_add 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_add completely? +

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

vault_add is provided by the Vault MCP server (zerocreds-com/zerocreds-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.