crow_backend_schema

THE RISK

Low Risk

Why crow_backend_schema needs a policy

This tool queries and displays metadata about backend tools and their schemas. It performs information retrieval with no ability to modify, delete, or execute operations. The worst-case scenario for misuse would be information disclosure about available backend tools, which is a low-severity risk in a well-architected system where schema information is not inherently sensitive.

From the tool's definition Tool name 'crow_backend_schema' with description 'Show discovered tools and schema for a data backend' indicates retrieval and display of schema information.

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

POLICY

How to control crow_backend_schema

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_backend_schema:

policy.json

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

crow_backend_schema 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 Crow — 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

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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 crow_backend_schema

What does the crow_backend_schema tool do? +

Show discovered tools and schema for a data backend. It is categorised as a Read tool in the Crow MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on crow_backend_schema? +

Register the Crow MCP server in PolicyLayer and add a rule for crow_backend_schema: 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_backend_schema? +

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

Can I rate-limit crow_backend_schema? +

Yes. Add a rate_limit block to the crow_backend_schema 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_backend_schema completely? +

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

crow_backend_schema 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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