add_activity_reply · Huly MCP: Risk & Policy

WHAT IT DOES

What add_activity_reply does on Huly

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

WHY IT NEEDS A POLICY

Why add_activity_reply needs a policy

An AI agent can call add_activity_reply faster than any human can review — one bad instruction and it creates or modifies resources in Huly by the hundred, each call as confident as the last.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_activity_reply Rate-limited

add_activity_reply 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": {
    "add_activity_reply": {
      "limits": [
        {
          "counter": "add_activity_reply_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 Huly, so you can run agents against it safely.

FAQ

Questions about add_activity_reply

What does the add_activity_reply tool do? +

Add a Markdown reply to any activity message. It is categorised as a Write tool in the Huly MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on add_activity_reply? +

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

What risk level is add_activity_reply? +

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

Can I rate-limit add_activity_reply? +

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

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

add_activity_reply is provided by the Huly MCP server (@firfi/huly-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.