Decompile a mod JAR file to readable Java source code. The JAR can be either the original mod JAR (with intermediary mappings) or a remapped JAR (from remap_mod_jar). Decompiled sources are cached in AppData/decompiled-mods/{modId}/{modVersion}/{mapping}/. Mod ID and version are auto-detected fro...
AI agents invoke decompile_mod_jar to trigger actions in Minecraft Dev 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.
This tool executes a decompilation process on an arbitrary JAR file path provided by the user, running external decompiler tooling and writing output to the filesystem. It spans Execute (running a decompiler process) and Write (caching results to disk). Per the rules, Execute is more severe than Write, and the tool triggers an external operation whose effects depend on the input JAR path argument.
From the tool's definition Decompile a mod JAR file to readable Java source code... Decompiled sources are cached in AppData/decompiled-mods/...
Documented attack patterns abuse exactly the kind of access decompile_mod_jar gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Minecraft Dev MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for decompile_mod_jar:
{
"version": "1",
"default": "deny",
"tools": {
"decompile_mod_jar": {
"limits": [
{
"counter": "decompile_mod_jar_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}decompile_mod_jar 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.
Free to start. No card required.
Decompile a mod JAR file to readable Java source code. The JAR can be either the original mod JAR (with intermediary mappings) or a remapped JAR (from remap_mod_jar). Decompiled sources are cached in AppData/decompiled-mods/{modId}/{modVersion}/{mapping}/. Mod ID and version are auto-detected from the JAR metadata if not provided. Supports both WSL (/mnt/c/...) and Windows (C:\\...) paths. It is categorised as a Execute tool in the Minecraft Dev MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Minecraft Dev MCP server in PolicyLayer and add a rule for decompile_mod_jar: 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 Dev MCP. Nothing to install.
decompile_mod_jar is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the decompile_mod_jar 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.
Set action: deny in the PolicyLayer policy for decompile_mod_jar. 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.
decompile_mod_jar is provided by the Minecraft Dev MCP server (mcdxai/minecraft-dev-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Minecraft Dev MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
20 Minecraft Dev MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.