memstem_upsert · Memstem MCP: Risk & Policy

WHAT IT DOES

What memstem_upsert does on Memstem

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

WHY IT NEEDS A POLICY

Why memstem_upsert needs a policy

Upsert operations create or modify data in a memory store. This is reversible (data can be corrected, deleted, or overwritten later), so it falls under Write rather than Destructive. The severity is medium because misuse could corrupt shared memory state affecting multiple AI agents, but the blast radius is contained to memory/data rather than external systems or finances.

From the tool's definition Tool name 'memstem_upsert' indicates an update or insert operation. Upsert semantics combine create and modify operations, which are Write category actions. The empty description limits precision but the name strongly suggests a reversible data modification.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

memstem_upsert Rate-limited

memstem_upsert 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": {
    "memstem_upsert": {
      "limits": [
        {
          "counter": "memstem_upsert_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 Memstem, so you can run agents against it safely.

FAQ

Questions about memstem_upsert

What does the memstem_upsert tool do? +

memstem_upsert. It is categorised as a Write tool in the Memstem MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on memstem_upsert? +

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

What risk level is memstem_upsert? +

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

Can I rate-limit memstem_upsert? +

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

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

memstem_upsert is provided by the Memstem MCP server (memstem/memstem). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.