hydrate_shelf · Shelv MCP Server MCP: Risk & Policy

WHAT IT DOES

What hydrate_shelf does on Shelv MCP Server

AI agents use hydrate_shelf to create or update resources in Shelv MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Shelv MCP Server environment.

WHY IT NEEDS A POLICY

Why hydrate_shelf needs a policy

The tool creates or modifies files locally, which is characteristic of Write category operations. It does not delete data irreversibly (Destructive), execute arbitrary code (Execute), or move money (Financial).

From the tool's definition Tool description explicitly states 'Download and write shelf files into a local directory'—the 'write' action indicates file creation or modification. The action is reversible (files can be deleted or overwritten later).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

hydrate_shelf Rate-limited

hydrate_shelf 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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Shelv MCP Server, so you can run agents against it safely.

FAQ

Questions about hydrate_shelf

What does the hydrate_shelf tool do? +

Download and write shelf files into a local directory. It is categorised as a Write tool in the Shelv MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on hydrate_shelf? +

Register the Shelv MCP Server MCP server in PolicyLayer and add a rule for hydrate_shelf: 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 Shelv MCP Server. Nothing to install.

What risk level is hydrate_shelf? +

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

Can I rate-limit hydrate_shelf? +

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

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

hydrate_shelf is provided by the Shelv MCP Server MCP server (shelv-dev/shelv-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.