play_trajectory · Vmd MCP: Risk & Policy

WHAT IT DOES

What play_trajectory does on Vmd

AI agents invoke play_trajectory to trigger actions in Vmd. 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 play_trajectory needs a policy

This tool triggers an external operation (animation playback) in the VMD2 application. It does not delete or overwrite data, move money, or simply read/write data passively — it executes a dynamic action in the visualization software. Severity is low because misuse has minimal blast radius beyond computational resource usage.

From the tool's definition 'Animate the trajectory of a molecule between two frames' — triggers an animation/playback operation in VMD2

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

play_trajectory Rate-limited

play_trajectory 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": {
    "play_trajectory": {
      "limits": [
        {
          "counter": "play_trajectory_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 Vmd, so you can run agents against it safely.

FAQ

Questions about play_trajectory

What does the play_trajectory tool do? +

Animate the trajectory of a molecule between two frames. It is categorised as a Execute tool in the Vmd MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on play_trajectory? +

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

What risk level is play_trajectory? +

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

Can I rate-limit play_trajectory? +

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

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

play_trajectory is provided by the Vmd MCP server (omararias-gaguancela/vmd-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.