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

WHAT IT DOES

What cache_add does on AWS IoT SiteWise MCP Server

AI agents use cache_add 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 cache_add needs a policy

This tool creates or modifies cached data, which is a reversible write operation. While caching impacts performance and potentially data consistency, it does not delete data, execute arbitrary code, or have financial implications.

From the tool's definition Tool name 'cache_add' and description 'Add a value to the cache' indicates creation/modification of data in a cache store. The conditional 'only if the key doesn't exist' shows it performs a reversible write operation without destructive intent.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

cache_add Rate-limited

cache_add 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": {
    "cache_add": {
      "limits": [
        {
          "counter": "cache_add_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 cache_add

What does the cache_add tool do? +

Add a value to the cache only if the key doesn't exist. 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 cache_add? +

Register the AWS IoT SiteWise MCP Server MCP server in PolicyLayer and add a rule for cache_add: 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 cache_add? +

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

Can I rate-limit cache_add? +

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

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

cache_add 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.