heartbeat

THE RISK

Medium Risk

Why heartbeat needs a policy

This tool writes/updates a status record (online presence/heartbeat signal) on the server. It modifies state but in a trivially reversible and low-impact way — it simply marks an agent as active. Misuse has minimal blast radius, hence low severity.

From the tool's definition 'Update your online status. Call periodically to show you are active.'

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

POLICY

How to control heartbeat

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "heartbeat": {
      "limits": [
        {
          "counter": "heartbeat_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

heartbeat 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.

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

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Brainstorm tools

Destructive delete_project Delete a project. Only the agent that created the project can delete it. Destructive delete_resource Delete a resource from the project. Only the resource creator can delete it. Write handover_coordinator Transfer coordinator role to another member. Only current coordinator can initiate. Target Write join_project Join a project with agent name. Session must be initialized by calling status tool first. Write leave_project Leave a project gracefully. Archives your unread messages and removes your membership. You Write store_resource Store shared resource. Use content for <50KB, source_path for >50KB (max 500KB). With sour Write archive_project Mark a project as archived (inactive but recoverable). Only the project creator can archiv Write create_project Create a new cooperation project. Projects are the organizing unit for agent collaboration

All 17 Brainstorm tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about heartbeat

What does the heartbeat tool do? +

Update your online status. Call periodically to show you are active. It is categorised as a Write tool in the Brainstorm MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on heartbeat? +

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

What risk level is heartbeat? +

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

Can I rate-limit heartbeat? +

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

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

heartbeat is provided by the Brainstorm MCP server (theodorstorm/brainstorm-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Brainstorm tool call.

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

CHECK YOUR STACK →