hll_add

THE RISK

Medium Risk

Why hll_add needs a policy

The 'add' operation modifies a HyperLogLog by inserting an element, which is a reversible write operation. While HyperLogLog modifications are typically non-destructive (elements can theoretically be removed or the structure reset), the tool performs data modification. This is classified as Write rather than Read because it has side effects that alter state.

From the tool's definition Tool name 'hll_add' and description 'Add one element to a HyperLogLog' indicate a data modification operation that appends/adds to a HyperLogLog data structure.

Documented attack patterns abuse exactly the kind of access hll_add gives an agent:

POLICY

How to control hll_add

PolicyLayer is an MCP gateway — it sits between your AI agents and Amazon Redshift MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for hll_add:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "hll_add": {
      "limits": [
        {
          "counter": "hll_add_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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.

Create a free account and register Amazon Redshift MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Amazon Redshift MCP Server tools

Destructive bulk_delete_by_criteria bulk_delete_by_criteria Destructive cache_delete Delete a value from the cache. Destructive cache_delete_many Delete multiple values from the cache. Destructive cache_delete_multi Delete multiple values from the cache (alias for delete_many). Destructive delete delete Destructive delete_access_key delete_access_key Destructive delete_agent_runtime delete_agent_runtime Destructive delete_agent_runtime_endpoint delete_agent_runtime_endpoint

All 805 Amazon Redshift MCP Server tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

Go deeper

Govern customer-ops agents → PII redaction, approval on external messages, and no-bulk-delete rules on the records agents change.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →
PolicyLayer vs alternatives → How deterministic, per-call MCP policy compares with gateways, identity layers, and authorisation platforms.

FAQ

Questions about hll_add

What does the hll_add tool do? +

Add one element to a HyperLogLog. It is categorised as a Write tool in the Amazon Redshift 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 hll_add? +

Register the Amazon Redshift MCP Server 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 Amazon Redshift MCP Server. 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 Amazon Redshift MCP Server MCP server (awslabs.redshift-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Amazon Redshift MCP Server tool call.

Start from Amazon Redshift MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →