list_length

Get length of list. Args: key: The name of the key Returns: Length or error message

SERVERAWS SOURCE@awslabs/mcp

Low RISK CLASS

Category Read

Parameters 00 required

Recommended Allowedsee the rule below

Registry record Grade F, identity verified Pull the record →

This record as markdown: /tools/aws/list-length.md

WHAT IT DOES

What list_length does on AWS

AI agents call list_length to retrieve information from AWS without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

RISK

Why list_length is rated Low

The tool performs a read-only operation (getting the length of a list) with no side effects. It queries data and returns information only. No data is created, modified, deleted, or executed. This is a straightforward Read category tool with low risk—misuse would only result in information disclosure about list sizes.

From the tool's definition Tool description states 'Get length of list' with an argument 'key: The name of the key' and returns 'Length or error message'. This is a query operation that retrieves metadata about a data structure without modifying, deleting, or executing arbitrary code.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs list_length 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 list_length, this is the rule to start with:

list_length Allowed

list_length is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "list_length": {}
  }
}

ALLOW ONLY THIS TOOL → Instant setup, no code required.

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

FAQ

Questions about list_length

What does the list_length tool do? +

Get length of list. Args: key: The name of the key Returns: Length or error message. It is categorised as a Read tool in the AWS MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_length? +

Register the AWS MCP server in PolicyLayer and add a rule for list_length: 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 list_length? +

list_length is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit list_length? +

Yes. Add a rate_limit block to the list_length 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_length completely? +

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

list_length 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.

KEEP EXPLORING

More on AWS, and thousands of servers like it.

This server

All 300 AWS tools →

Across the catalogue

aiva_list_affiliates on AIVA MCP Server →list_circuits on 0gzk →list_agents on 0rca Dojo MCP Server → The MCP Attack Database →

Guides

Roll out MCP under one policy →Data exfiltration →MCP token cost →