set_username · Tenzro Ledger MCP: Risk & Policy

WHAT IT DOES

What set_username does on Tenzro Ledger MCP

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

WHY IT NEEDS A POLICY

Why set_username needs a policy

This tool modifies identity metadata (username associated with a DID) but does not delete data, execute code, move funds, or trigger external operations. It is reversible (the username can be changed).

From the tool's definition Tool description states it 'Set[s] a human-readable username for a DID' — a create/modify operation on identity data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_username Rate-limited

set_username 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": {
    "set_username": {
      "limits": [
        {
          "counter": "set_username_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 Tenzro Ledger MCP, so you can run agents against it safely.

FAQ

Questions about set_username

What does the set_username tool do? +

Set a human-readable username for a DID. It is categorised as a Write tool in the Tenzro Ledger MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on set_username? +

Register the Tenzro Ledger MCP server in PolicyLayer and add a rule for set_username: 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 Tenzro Ledger MCP. Nothing to install.

What risk level is set_username? +

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

Can I rate-limit set_username? +

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

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

set_username is provided by the Tenzro Ledger MCP server (https://canton-mcp.tenzro.network/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.