hll_add

Add one element to a HyperLogLog. Args: key: The name of the HyperLogLog key element: One element to add Returns: Success message or error message

SERVERAWS SOURCE@awslabs/mcp

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity verified Pull the record →

This record as markdown: /tools/aws/hll-add.md

WHAT IT DOES

What hll_add does on AWS

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

RISK

Why hll_add is rated Medium

This tool creates or modifies data reversibly by adding an element to an in-memory or stored HyperLogLog structure. The operation is not destructive (no deletion), does not execute arbitrary code, and has minimal blast radius if misused by an AI agent—it would only add cardinality estimates to a counter. This is a typical Write operation.

From the tool's definition Tool name 'hll_add' and description 'Add one element to a HyperLogLog' indicate a data modification operation. HyperLogLog is a probabilistic data structure used for cardinality estimation, and 'add' modifies its state by inserting an element.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs hll_add safely

PolicyLayer is an MCP gateway: it sits between your AI agents and AWS, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For hll_add, this is the rule to start with:

hll_add Rate-limited

hll_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": {
    "hll_add": {
      "limits": [
        {
          "counter": "hll_add_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect AWS, apply this rule, and every hll_add call is checked against it from then on.

FAQ

Questions about hll_add

What does the hll_add tool do? +

Add one element to a HyperLogLog. Args: key: The name of the HyperLogLog key element: One element to add Returns: Success message or error message. It is categorised as a Write tool in the AWS MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on hll_add? +

Register the AWS MCP server in PolicyLayer and add a rule for hll_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. Nothing to install.

What risk level is hll_add? +

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

Can I rate-limit hll_add? +

Yes. Add a rate_limit block to the hll_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 hll_add completely? +

Set action: deny in the PolicyLayer policy for hll_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 hll_add? +

hll_add is provided by the AWS MCP server (@awslabs/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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