fleet_nginx_add

THE RISK

Medium Risk

Why fleet_nginx_add needs a policy

The tool creates Nginx configuration files for domains, which is a Write operation—it generates new configuration that affects production web server behavior. Severity is high because misconfigured Nginx can disrupt service availability, expose sensitive headers, or create security vulnerabilities (e.g., incorrect CORS, TLS settings, or routing), but the operation itself is not destructive (configs can be…

From the tool's definition Tool name 'fleet_nginx_add' and description 'Create an nginx config for a domain' indicate creation of configuration data. This is a reversible modification operation (configs can be updated or deleted).

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

POLICY

How to control fleet_nginx_add

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

policy.json

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

fleet_nginx_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.

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

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Fleet tools

Execute fleet_audit_run Run an App Store compliance audit on a mobile app project via greenlight preflight. Execute fleet_deploy Deploy an app: build and restart Execute fleet_secrets_unseal Decrypt vault to /run/fleet-secrets/. WARNING: This overwrites any runtime changes that we Execute fleet_deps_scan Run a fresh dependency scan across all registered apps Execute fleet_git_push Push current branch to origin Write fleet_deps_fix Create a PR with dependency updates for an app (dry-run by default) Write fleet_audit_ignore Suppress a confirmed greenlight false positive from future audits. The finding is Write fleet_secrets_seal Seal runtime secrets back to the encrypted vault.

All 39 Fleet tools →

Write tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about fleet_nginx_add

What does the fleet_nginx_add tool do? +

Create an nginx config for a domain. It is categorised as a Write tool in the Fleet MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on fleet_nginx_add? +

Register the Fleet MCP server in PolicyLayer and add a rule for fleet_nginx_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 Fleet. Nothing to install.

What risk level is fleet_nginx_add? +

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

Can I rate-limit fleet_nginx_add? +

Yes. Add a rate_limit block to the fleet_nginx_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 fleet_nginx_add completely? +

Set action: deny in the PolicyLayer policy for fleet_nginx_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 fleet_nginx_add? +

fleet_nginx_add is provided by the Fleet MCP server (wrxck/fleet). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Fleet tool call.

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

CHECK YOUR STACK →