crow_set_background

THE RISK

Medium Risk

Why crow_set_background needs a policy

This tool creates or modifies application state (the active background setting) in a reversible manner. It does not retrieve data (Read), execute arbitrary code (Execute), delete anything (Destructive), move money (Financial), or trigger external side effects. The change is easily undone by setting a different background.

From the tool's definition Tool description explicitly states 'Set a previously generated gallery image as the current companion background' — this modifies a display/UI setting by changing which background image is active.

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

POLICY

How to control crow_set_background

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_set_background:

policy.json

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

crow_set_background 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 →

Free to start. No card required.

EXPLORE

Related tools and policies

More Crow tools

Financial crow_tax_prepare_from_documents One-step tax return preparation: creates a return from ALL confirmed documents uploaded th Financial crow_actual_create_transaction Create a new transaction. Amount in cents (negative = expense, positive = income). Financial crow_tax_set_capital_gains Add Schedule D capital gain/loss transactions. Destructive caddy_remove_site Remove a site block from the Caddyfile (matched by address) and reload Caddy. Destructive Destructive crow_bookstack_delete Delete a page or chapter from BookStack (irreversible) Destructive crow_campaign_delete Delete a campaign and all its posts. Requires confirmation. Destructive crow_crosspost_cancel Cancel a queued cross-post before its scheduled_at fires. Idempotent — cancelling an alrea Destructive crow_delete_context_section Delete a custom crow.md section. Protected sections cannot be deleted — only disabled. Sco

All 576 Crow 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 crow_set_background

What does the crow_set_background tool do? +

Set a previously generated gallery image as the current companion background. 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_set_background? +

Register the Crow MCP server in PolicyLayer and add a rule for crow_set_background: 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_set_background? +

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

Can I rate-limit crow_set_background? +

Yes. Add a rate_limit block to the crow_set_background 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_set_background completely? +

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

crow_set_background 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.

CHECK YOUR STACK →