nexus_register_spec · NexusToken MCP: Risk & Policy

WHAT IT DOES

What nexus_register_spec does on NexusToken

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

WHY IT NEEDS A POLICY

Why nexus_register_spec needs a policy

This tool creates or publishes new capability specifications to a catalog, which is a reversible data modification operation. It doesn't execute external commands, delete data permanently, or move money.

From the tool's definition Tool name 'nexus_register_spec' and description 'publish a new CapabilitySpec to the catalog' indicate creation/modification of catalog data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

nexus_register_spec Rate-limited

nexus_register_spec 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": {
    "nexus_register_spec": {
      "limits": [
        {
          "counter": "nexus_register_spec_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 NexusToken, so you can run agents against it safely.

FAQ

Questions about nexus_register_spec

What does the nexus_register_spec tool do? +

Provider tool: publish a new CapabilitySpec to the catalog so. It is categorised as a Write tool in the NexusToken MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on nexus_register_spec? +

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

What risk level is nexus_register_spec? +

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

Can I rate-limit nexus_register_spec? +

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

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

nexus_register_spec is provided by the NexusToken MCP server (bobuilds/nexustoken-sdk). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.