create_ref · Substrate MCP: Risk & Policy

WHAT IT DOES

What create_ref does on Substrate

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

WHY IT NEEDS A POLICY

Why create_ref needs a policy

This tool creates or updates references, which is a write operation that can be undone or modified later. It does not execute code, delete data irreversibly, or move money. The medium severity reflects that it modifies stored data and could impact system state if misused to create unwanted references, but the changes are not permanent or destructive.

From the tool's definition Tool description states 'Create or update a reference' — these are reversible write operations that modify data without permanent deletion.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_ref Rate-limited

create_ref 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": {
    "create_ref": {
      "limits": [
        {
          "counter": "create_ref_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 Substrate, so you can run agents against it safely.

FAQ

Questions about create_ref

What does the create_ref tool do? +

Create or update a reference. It is categorised as a Write tool in the Substrate MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on create_ref? +

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

What risk level is create_ref? +

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

Can I rate-limit create_ref? +

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

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

create_ref is provided by the Substrate MCP server (ivan-saorin/substrate). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.