vercel_list_env_vars

THE RISK

Low Risk

Why vercel_list_env_vars needs a policy

This tool retrieves and queries existing environment variables without creating, modifying, deleting, or executing anything. It is a straightforward data retrieval operation, making it a Read category tool with low severity since listing configuration does not directly impact system integrity or enable further attacks without additional privileges.

From the tool's definition Tool name 'vercel_list_env_vars' and description 'List environment variables for a project' indicate a query/retrieval operation with no side effects.

Documented attack patterns abuse exactly the kind of access vercel_list_env_vars gives an agent:

POLICY

How to control vercel_list_env_vars

PolicyLayer is an MCP gateway — it sits between your AI agents and Vercel, and nothing reaches the server without passing your rules. This is the rule we recommend for vercel_list_env_vars:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "vercel_list_env_vars": {}
  }
}

vercel_list_env_vars is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Vercel — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

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EXPLORE

Related tools and policies

More Vercel tools

Destructive vercel_cancel_deployment Cancel a deployment that is currently building Destructive vercel_delete_domain Delete a domain Destructive vercel_delete_env_var Delete an environment variable Write vercel_add_domain Add a new domain Write vercel_create_env_var Create a new environment variable for a project Write vercel_update_env_var Update an existing environment variable Read vercel_get_deployment Get details of a specific deployment Read vercel_get_deployment_logs Get logs for a specific deployment

All 13 Vercel tools →

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about vercel_list_env_vars

What does the vercel_list_env_vars tool do? +

List environment variables for a project. It is categorised as a Read tool in the Vercel MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on vercel_list_env_vars? +

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

What risk level is vercel_list_env_vars? +

vercel_list_env_vars is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit vercel_list_env_vars? +

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

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

vercel_list_env_vars is provided by the Vercel MCP server (xiayeai/vercel-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Vercel tool call.

Start from Vercel, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

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