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

WHAT IT DOES

What hash_set does on AWS IoT SiteWise MCP Server

AI agents use hash_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 hash_set needs a policy

This tool performs a reversible write operation by setting/modifying a field within a hash data structure. It does not delete data (ruling out Destructive), execute arbitrary code (ruling out Execute), or involve financial transactions (ruling out Financial).

From the tool's definition Tool description states 'Set field in hash' which indicates modification of data structure fields. The verb 'set' confirms a write operation that creates or modifies data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

hash_set Rate-limited

hash_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": {
    "hash_set": {
      "limits": [
        {
          "counter": "hash_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 hash_set

What does the hash_set tool do? +

Set field in hash. 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 hash_set? +

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

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

Can I rate-limit hash_set? +

Yes. Add a rate_limit block to the hash_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 hash_set completely? +

Set action: deny in the PolicyLayer policy for hash_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 hash_set? +

hash_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.