merge_pdfs · Nexus Core MCP: Risk & Policy

WHAT IT DOES

What merge_pdfs does on Nexus Core

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

WHY IT NEEDS A POLICY

Why merge_pdfs needs a policy

The tool creates or modifies data (a new PDF file) in a reversible manner—the merged PDF can be deleted or recreated. This fits the Write category (creates/modifies data reversibly) rather than Read (no side effects) or Destructive (irreversible deletion).

From the tool's definition The tool description states it will 'Concatenate multiple PDFs into output_path, in order,' which creates a new file by merging input files. This is a file creation/modification operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

merge_pdfs Rate-limited

merge_pdfs 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": {
    "merge_pdfs": {
      "limits": [
        {
          "counter": "merge_pdfs_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 Nexus Core, so you can run agents against it safely.

FAQ

Questions about merge_pdfs

What does the merge_pdfs tool do? +

Concatenate multiple PDFs into output_path, in order. It is categorised as a Write tool in the Nexus Core MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on merge_pdfs? +

Register the Nexus Core MCP server in PolicyLayer and add a rule for merge_pdfs: 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 Nexus Core. Nothing to install.

What risk level is merge_pdfs? +

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

Can I rate-limit merge_pdfs? +

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

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

merge_pdfs is provided by the Nexus Core MCP server (noumenon-ai/nexus-core). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.