kg_assert · Predicate MCP: Risk & Policy

WHAT IT DOES

What kg_assert does on Predicate

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

WHY IT NEEDS A POLICY

Why kg_assert needs a policy

This tool creates/inserts new data (a triple) into the knowledge graph. Asserting a triple is a write operation - it adds new information with provenance metadata. It is reversible (can be retracted/demoted, as suggested by the sibling 'kg_demote' tool), so it falls under Write rather than Destructive.

From the tool's definition Assert a triple into kg:abox with RDF-star provenance (source, confidence, method)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

kg_assert Rate-limited

kg_assert 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": {
    "kg_assert": {
      "limits": [
        {
          "counter": "kg_assert_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 Predicate, so you can run agents against it safely.

FAQ

Questions about kg_assert

What does the kg_assert tool do? +

Assert a triple into kg:abox with RDF-star provenance (source, confidence, method). It is categorised as a Write tool in the Predicate MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on kg_assert? +

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

What risk level is kg_assert? +

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

Can I rate-limit kg_assert? +

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

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

kg_assert is provided by the Predicate MCP server (nordicagents/predicate). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.