store_update · Willow MCP: Risk & Policy

WHAT IT DOES

What store_update does on Willow

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

WHY IT NEEDS A POLICY

Why store_update needs a policy

The store_update tool performs a reversible modification of existing data (updates). It does not delete, destroy, or irreversibly overwrite data, nor does it create new records. The audit-trailing mentioned indicates changeability is tracked, supporting the Write classification.

From the tool's definition Tool description states 'Update an existing record in-place' and 'Use store_put to create new records', indicating this tool modifies existing data reversibly rather than creating new records or deleting data.

Risk signalsBulk/mass operation — affects multiple targets

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

store_update Rate-limited

store_update 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": {
    "store_update": {
      "limits": [
        {
          "counter": "store_update_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 Willow, so you can run agents against it safely.

FAQ

Questions about store_update

What does the store_update tool do? +

Update an existing record in-place. Every update is audit-trailed with the previous value. Use store_put to create new records. It is categorised as a Write tool in the Willow MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on store_update? +

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

What risk level is store_update? +

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

Can I rate-limit store_update? +

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

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

store_update is provided by the Willow MCP server (rudi193-cmd/willow-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.