enter_market · Justlend MCP: Risk & Policy

WHAT IT DOES

What enter_market does on Justlend

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

WHY IT NEEDS A POLICY

Why enter_market needs a policy

This tool modifies the user's account state on JustLend by enabling a market as collateral. It is a reversible configuration change (markets can typically be exited), so it falls under Write rather than Execute or Destructive. However, misuse could indirectly enable borrowing against assets, increasing financial risk exposure, hence medium severity.

From the tool's definition Enable a jToken market as collateral. Required before borrowing against supplied assets.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

enter_market Rate-limited

enter_market 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": {
    "enter_market": {
      "limits": [
        {
          "counter": "enter_market_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 Justlend, so you can run agents against it safely.

FAQ

Questions about enter_market

What does the enter_market tool do? +

Enable a jToken market as collateral. Required before borrowing against supplied assets. It is categorised as a Write tool in the Justlend MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on enter_market? +

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

What risk level is enter_market? +

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

Can I rate-limit enter_market? +

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

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

enter_market is provided by the Justlend MCP server (justlend/mcp-server-justlend). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.