start_phonons · Fairchem MCP: Risk & Policy

WHAT IT DOES

What start_phonons does on Fairchem

AI agents invoke start_phonons to trigger actions in Fairchem. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why start_phonons needs a policy

Phonon analysis is a physics simulation that runs code/external operations via FAIRChem/ASE whose effects depend on the structure and parameters passed to it. This is not a read operation (it triggers computation), not write (it doesn't modify data reversibly—it generates new results), and not destructive (nothing is deleted).

From the tool's definition Tool named 'start_phonons' on a server that 'allows LLM agents to...steer relaxations, MD, NEB, phonons, and minima searches mid-flight'.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

start_phonons Rate-limited

start_phonons stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "start_phonons": {
      "limits": [
        {
          "counter": "start_phonons_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Fairchem, so you can run agents against it safely.

FAQ

Questions about start_phonons

What does the start_phonons tool do? +

start_phonons. It is categorised as a Execute tool in the Fairchem MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on start_phonons? +

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

What risk level is start_phonons? +

start_phonons is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit start_phonons? +

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

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

start_phonons is provided by the Fairchem MCP server (jkitchin/fairchem-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.