jsr_create_package_version · JSR MCP: Risk & Policy

WHAT IT DOES

What jsr_create_package_version does on JSR MCP

AI agents use jsr_create_package_version to create or update resources in JSR MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your JSR MCP environment.

WHY IT NEEDS A POLICY

Why jsr_create_package_version needs a policy

This tool creates and uploads new package versions to the JSR registry. While it is reversible (versions could be deleted or deprecated), it represents a significant write operation that modifies the registry state and makes code available to potentially many users. The write category applies because the primary effect is creation/addition of data.

From the tool's definition "Create a new package version by uploading a tarball" — this creates new versioned artifacts in the registry, modifying the package catalog.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

jsr_create_package_version Rate-limited

jsr_create_package_version stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "jsr_create_package_version": {
      "limits": [
        {
          "counter": "jsr_create_package_version_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches JSR MCP, so you can run agents against it safely.

FAQ

Questions about jsr_create_package_version

What does the jsr_create_package_version tool do? +

Create a new package version by uploading a tarball (requires authentication and scope membership). It is categorised as a Write tool in the JSR MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on jsr_create_package_version? +

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

What risk level is jsr_create_package_version? +

jsr_create_package_version is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit jsr_create_package_version? +

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

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

jsr_create_package_version is provided by the JSR MCP server (wyattjoh/jsr-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.