kg_propose_schema · Predicate MCP: Risk & Policy

WHAT IT DOES

What kg_propose_schema does on Predicate

AI agents use kg_propose_schema 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_propose_schema needs a policy

kg_propose_schema creates or modifies schema proposals in a staging area (kg:tbox-staging) with associated metadata and event emission. This is a reversible write operation—proposals in staging can be reviewed before promotion and are not final until swept/promoted by a separate process. The tool does not execute arbitrary code, delete data irreversibly, or move money.

From the tool's definition Writes to kg:tbox-staging with metadata; emits a SchemaProposed event. Promotion is the sweeper

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

kg_propose_schema Rate-limited

kg_propose_schema 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_propose_schema": {
      "limits": [
        {
          "counter": "kg_propose_schema_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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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_propose_schema

What does the kg_propose_schema tool do? +

Stage a SchemaDelta proposal (add-class, add-property, refine-class, or breaking). Writes to kg:tbox-staging with metadata; emits a SchemaProposed event. Promotion is the sweeper. 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_propose_schema? +

Register the Predicate MCP server in PolicyLayer and add a rule for kg_propose_schema: 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_propose_schema? +

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

Can I rate-limit kg_propose_schema? +

Yes. Add a rate_limit block to the kg_propose_schema 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_propose_schema completely? +

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

kg_propose_schema 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.