save_decision · Nexus Core MCP: Risk & Policy

WHAT IT DOES

What save_decision does on Nexus Core

AI agents use save_decision 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 save_decision needs a policy

This tool writes decision records to persistent storage but the operation is reversible (decisions can be edited or deleted), has no external side effects, and affects only user-owned data. The impact is localized to a personal decision log without financial, destructive, or code-execution implications.

From the tool's definition Tool performs 'Log an architectural / life decision' which creates or records new data entries in a decision log. The verb 'log' indicates data creation/writing rather than retrieval or execution of external operations.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

save_decision Rate-limited

save_decision 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": {
    "save_decision": {
      "limits": [
        {
          "counter": "save_decision_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 save_decision

What does the save_decision tool do? +

Log an architectural / life decision. Date defaults to today (UTC). 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 save_decision? +

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

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

Can I rate-limit save_decision? +

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

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

save_decision 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.