hermes_cancel

THE RISK

Low Risk

Why hermes_cancel needs a policy

The name suggests cancelling a task or operation delegated to the Hermes Agent. Cancellation could be a Write (stopping/modifying a running task) or Execute (triggering a cancel action), but without a description it's unclear. Sibling tools (ask, check, reset) suggest task management context. 'Cancel' most likely stops a running operation, which is a moderate-severity action.

From the tool's definition Tool name is 'hermes_cancel' but description is empty or uninformative.

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

POLICY

How to control hermes_cancel

PolicyLayer is an MCP gateway — it sits between your AI agents and Hermes, and nothing reaches the server without passing your rules. This is the rule we recommend for hermes_cancel:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "hermes_cancel": {
      "limits": [
        {
          "counter": "hermes_cancel_rate",
          "window": "minute",
          "max": 60,
          "scope": "grant"
        }
      ]
    }
  }
}

hermes_cancel gets a rate cap, and everything else on the server is denied unless you say otherwise.

Create a free account and register Hermes — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

SET A RULE FOR THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Hermes tools

Destructive hermes_reset hermes_reset Other hermes_ask hermes_ask Read hermes_check hermes_check

All 4 Hermes tools →

Other tools on other servers

Android Forensics ADB MCP Server generate_app_analysis_report Ethereum Tools add Math MCP Server complex_analysis_suite Crypto_MCP aes_encrypt

Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Tool risk categories → How PolicyLayer classifies MCP tools by what they can do.
MCP tool → What an MCP tool is and how clients discover and call it.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about hermes_cancel

What does the hermes_cancel tool do? +

hermes_cancel. It is categorised as a Other tool in the Hermes MCP Server, which means it performs auxiliary operations.

How do I enforce a policy on hermes_cancel? +

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

What risk level is hermes_cancel? +

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

Can I rate-limit hermes_cancel? +

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

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

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

Enforce policy on every Hermes tool call.

Start from Hermes, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →