list_set · AWS IoT SiteWise MCP Server MCP: Risk & Policy

WHAT IT DOES

What list_set does on AWS IoT SiteWise MCP Server

AI agents use list_set to create or update resources in AWS IoT SiteWise MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your AWS IoT SiteWise MCP Server environment.

WHY IT NEEDS A POLICY

Why list_set needs a policy

Despite the name 'list_set', the description explicitly states it sets (writes) a value at a specific index in a list, which is a data modification operation. This is a Write operation as it modifies existing data. Confidence is moderate because the description is brief and doesn't fully clarify the scope or irreversibility of the change, and the tool name/description mismatch raises some ambiguity.

From the tool's definition Tool description says 'Set value at index in list' — this modifies/overwrites a value in a list structure.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

list_set Rate-limited

list_set 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": {
    "list_set": {
      "limits": [
        {
          "counter": "list_set_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 AWS IoT SiteWise MCP Server, so you can run agents against it safely.

FAQ

Questions about list_set

What does the list_set tool do? +

Set value at index in list. It is categorised as a Write tool in the AWS IoT SiteWise MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on list_set? +

Register the AWS IoT SiteWise MCP Server MCP server in PolicyLayer and add a rule for list_set: 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 AWS IoT SiteWise MCP Server. Nothing to install.

What risk level is list_set? +

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

Can I rate-limit list_set? +

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

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

list_set is provided by the AWS IoT SiteWise MCP Server MCP server (awslabs.aws-iot-sitewise-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.