relation_create · Mementos MCP: Risk & Policy

WHAT IT DOES

What relation_create does on Mementos

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

WHY IT NEEDS A POLICY

Why relation_create needs a policy

This tool creates new relations in a memory system, which is a write operation that modifies data state but remains reversible (relations can be deleted via relation_delete or similar operations). The blast radius is medium because misuse could corrupt the agent's knowledge graph or create false semantic relationships, but the effects are confined to metadata and can be undone.

From the tool's definition Tool name 'relation_create' and description 'Create a relation between two entities' explicitly indicates data creation via a reversible operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

relation_create Rate-limited

relation_create 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": {
    "relation_create": {
      "limits": [
        {
          "counter": "relation_create_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Mementos, so you can run agents against it safely.

FAQ

Questions about relation_create

What does the relation_create tool do? +

Create a relation between two entities (uses, knows, depends_on, created_by, related_to, contradicts, part_of, implements). It is categorised as a Write tool in the Mementos MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on relation_create? +

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

What risk level is relation_create? +

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

Can I rate-limit relation_create? +

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

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

relation_create is provided by the Mementos MCP server (@hasna/mementos). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.