editor_evaluate_expression · Godot MCP: Risk & Policy

WHAT IT DOES

What editor_evaluate_expression does on Godot

AI agents invoke editor_evaluate_expression to trigger actions in Godot. 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.

PARAMETERS

Parameter	Type	Required	Description
`expression`	string	Yes	GDScript expression to evaluate

Parameters from the server's own tool schema.

WHY IT NEEDS A POLICY

Why editor_evaluate_expression needs a policy

This tool executes arbitrary GDScript code in the Godot editor/debugger context. Evaluating arbitrary expressions can trigger file system operations, spawn processes, modify project state, or cause other side effects depending on the expression provided. This is code execution, and misuse could have broad impact on the Godot project or host system.

From the tool's definition "Evaluate a GDScript expression in debugger/editor context"

Risk signalsAccepts freeform code/query input (expression)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

editor_evaluate_expression Rate-limited

editor_evaluate_expression 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": {
    "editor_evaluate_expression": {
      "limits": [
        {
          "counter": "editor_evaluate_expression_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 Godot, so you can run agents against it safely.

FAQ

Questions about editor_evaluate_expression

What does the editor_evaluate_expression tool do? +

Evaluate a GDScript expression in debugger/editor context. It is categorised as a Execute tool in the Godot MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

What parameters does editor_evaluate_expression accept? +

editor_evaluate_expression accepts 1 parameter: expression. Required: expression. The full parameter table on this page comes from the server's own tool schema.

How do I enforce a policy on editor_evaluate_expression? +

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

What risk level is editor_evaluate_expression? +

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

Can I rate-limit editor_evaluate_expression? +

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

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

editor_evaluate_expression is provided by the Godot MCP server (@yanhuifair/godot-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.