add_signature_to_pdf · Nexus Core MCP: Risk & Policy

WHAT IT DOES

What add_signature_to_pdf does on Nexus Core

AI agents use add_signature_to_pdf 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 add_signature_to_pdf needs a policy

This tool modifies a PDF by adding content (a signature image) to it. While reversible (the overlay could theoretically be removed), it alters the document's state and is a Write operation. It does not execute arbitrary code, delete data, or move funds.

From the tool's definition Tool description explicitly states it performs an 'Overlay a signature image on a specific page + (x,y) of a PDF', which modifies the PDF document.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_signature_to_pdf Rate-limited

add_signature_to_pdf 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": {
    "add_signature_to_pdf": {
      "limits": [
        {
          "counter": "add_signature_to_pdf_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 add_signature_to_pdf

What does the add_signature_to_pdf tool do? +

Overlay a signature image on a specific page + (x,y) of a PDF. Visual overlay only — NOT cryptographic. 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 add_signature_to_pdf? +

Register the Nexus Core MCP server in PolicyLayer and add a rule for add_signature_to_pdf: 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 add_signature_to_pdf? +

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

Can I rate-limit add_signature_to_pdf? +

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

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

add_signature_to_pdf 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.