steer · Fairchem MCP: Risk & Policy

WHAT IT DOES

What steer does on Fairchem

AI agents invoke steer 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 steer needs a policy

Steering mid-flight simulations is an Execute action because it triggers control over external operations (computational chemistry simulations) whose effects depend on arguments and cannot be simply reversed. While the description is empty, the server context makes the purpose clear.

From the tool's definition Tool name is 'steer' on a server that 'allows LLM agents to load a model once and steer relaxations, MD, NEB, phonons, and minima searches mid-flight.' The server description indicates this tool directs or modifies ongoing computational simulations…

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

steer Rate-limited

steer 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": {
    "steer": {
      "limits": [
        {
          "counter": "steer_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 steer

What does the steer tool do? +

steer. 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 steer? +

Register the Fairchem MCP server in PolicyLayer and add a rule for steer: 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 steer? +

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

Can I rate-limit steer? +

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

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

steer 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.