crow_add_relay

THE RISK

Medium Risk

Why crow_add_relay needs a policy

The tool creates or modifies configuration by adding relays for messaging and file sharing. This is a reversible write operation (relays can be removed from configuration). It modifies system state but does not irreversibly delete data, execute arbitrary code, or move financial assets.

From the tool's definition Add a Nostr or peer relay to your configuration. Nostr relays handle encrypted messaging. Peer relays handle offline share delivery.

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

POLICY

How to control crow_add_relay

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

policy.json

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

crow_add_relay 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 Crow — 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 →

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EXPLORE

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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 crow_add_relay

What does the crow_add_relay tool do? +

Add a Nostr or peer relay to your configuration. Nostr relays handle encrypted messaging. Peer relays handle offline share delivery. It is categorised as a Write tool in the Crow MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on crow_add_relay? +

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

What risk level is crow_add_relay? +

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

Can I rate-limit crow_add_relay? +

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

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

crow_add_relay is provided by the Crow MCP server (kh0pper/crow). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Crow tool call.

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

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