extract_class_info

THE RISK

Low Risk

Why extract_class_info needs a policy

extract_class_info retrieves and returns metadata about Java classes (bytecode information, structure, signatures, etc.) without modifying the jar file, executing code, or triggering external operations. This is a straightforward read operation that queries the contents of an already-downloaded local jar file.

From the tool's definition Tool description states it 'Get[s] detailed information about Java classes in a jar' - a retrieval operation with no modification or execution.

Documented attack patterns abuse exactly the kind of access extract_class_info gives an agent:

POLICY

How to control extract_class_info

PolicyLayer is an MCP gateway — it sits between your AI agents and Maven Decoder MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for extract_class_info:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "extract_class_info": {}
  }
}

extract_class_info is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Maven Decoder MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Maven Decoder MCP Server tools

Read analyze_jar Analyze a specific jar file and extract detailed information Read analyze_jar_structure Analyze the overall structure and metadata of a jar file Read compare_versions Compare different versions of the same Maven artifact Read extract_jar_resource Extract text resources from a jar, such as .proto files, service descriptors, or metadata Read extract_method_info Extract specific method information from a Java class Read extract_source_code Extract source code from jar (if available) or decompile bytecode Read find_dependents Find artifacts that depend on a specific artifact Read find_usage_examples Find usage examples of classes/methods in test jars

All 14 Maven Decoder MCP Server tools →

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about extract_class_info

What does the extract_class_info tool do? +

Get detailed information about Java classes in a jar. It is categorised as a Read tool in the Maven Decoder MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on extract_class_info? +

Register the Maven Decoder MCP Server MCP server in PolicyLayer and add a rule for extract_class_info: 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 Maven Decoder MCP Server. Nothing to install.

What risk level is extract_class_info? +

extract_class_info is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit extract_class_info? +

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

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

extract_class_info is provided by the Maven Decoder MCP Server MCP server (salitaba/maven-decoder-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Maven Decoder MCP Server tool call.

Start from Maven Decoder MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →