hcs_topic · HashPilot MCP: Risk & Policy

WHAT IT DOES

What hcs_topic does on HashPilot

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

WHY IT NEEDS A POLICY

Why hcs_topic needs a policy

The create and update operations modify blockchain state by creating new HCS topics and updating topic configurations. While these changes are generally reversible (topics can be deleted or reconfigured), they represent Write operations that commit data to an immutable ledger and incur transaction costs. The subscribe operation is Read-only, but the tool's primary capability is Write.

From the tool's definition The tool performs operations that create and modify blockchain state: 'Create new public or private topic' and 'Update topic memo or auto-renew period'.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

hcs_topic Rate-limited

hcs_topic 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": {
    "hcs_topic": {
      "limits": [
        {
          "counter": "hcs_topic_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 HashPilot, so you can run agents against it safely.

FAQ

Questions about hcs_topic

What does the hcs_topic tool do? +

Hedera Consensus Service (HCS) topic management. OPERATIONS: - create: Create new public or private topic with configurable keys - update: Update topic memo or auto-renew period - subscribe: Subscribe to real-time topic messages USE THIS FOR: Creating consensus topics, configuring topic settings, real-time message streams. It is categorised as a Write tool in the HashPilot MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on hcs_topic? +

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

What risk level is hcs_topic? +

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

Can I rate-limit hcs_topic? +

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

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

hcs_topic is provided by the HashPilot MCP server (justmert/hashpilot). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.