fill_blocks · Minecraft Server MCP: Risk & Policy

WHAT IT DOES

What fill_blocks does on Minecraft Server MCP

AI agents invoke fill_blocks to trigger actions in Minecraft Server MCP. 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 fill_blocks needs a policy

This tool executes a Minecraft /fill command that can overwrite up to 32,768 blocks in a region. While it modifies world data (Write), it also can irreversibly destroy existing structures and terrain by replacing blocks — however, since Minecraft worlds can be backed up and the operation is not a permanent deletion per se, Execute is most appropriate.

From the tool's definition Fill a region with blocks. Uses the /fill command. Max 32,768 blocks per operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

fill_blocks Rate-limited

fill_blocks 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": {
    "fill_blocks": {
      "limits": [
        {
          "counter": "fill_blocks_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 Minecraft Server MCP, so you can run agents against it safely.

FAQ

Questions about fill_blocks

What does the fill_blocks tool do? +

Fill a region with blocks. Uses the /fill command. Max 32,768 blocks per operation. It is categorised as a Execute tool in the Minecraft Server MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on fill_blocks? +

Register the Minecraft Server MCP server in PolicyLayer and add a rule for fill_blocks: 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 Minecraft Server MCP. Nothing to install.

What risk level is fill_blocks? +

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

Can I rate-limit fill_blocks? +

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

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

fill_blocks is provided by the Minecraft Server MCP server (tamo2918/minecraft-server-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.