pin_fact · Headroom MCP: Risk & Policy

WHAT IT DOES

What pin_fact does on Headroom

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

WHY IT NEEDS A POLICY

Why pin_fact needs a policy

This tool creates or modifies a fact record that persists through context window management. It is a Write operation because it stores data with reversible effects (facts can be unpinned or replaced). It poses low severity because it only affects internal task metadata and planning state, not external systems or user data—misuse would degrade task coordination but not cause irreversible harm or data loss.

From the tool's definition Pin a fact... must survive context compaction VERBATIM — hard user constraints, deadlines, exact values. The tool writes/persists data (facts) into a managed state or memory structure.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

pin_fact Rate-limited

pin_fact 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": {
    "pin_fact": {
      "limits": [
        {
          "counter": "pin_fact_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 Headroom, so you can run agents against it safely.

FAQ

Questions about pin_fact

What does the pin_fact tool do? +

Pin a fact that must survive context compaction VERBATIM — hard user constraints, deadlines, exact values (. It is categorised as a Write tool in the Headroom MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on pin_fact? +

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

What risk level is pin_fact? +

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

Can I rate-limit pin_fact? +

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

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

pin_fact is provided by the Headroom MCP server (tyejcoleman/headroom). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.