set_cardinality
Get number of members in set. Args: key: The name of the key Returns: Number of members or error message
This record as markdown: /tools/aws/set-cardinality.md
What set_cardinality does on AWS
AI agents call set_cardinality 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.
Why set_cardinality is rated Low
This tool only retrieves the count of members in a set (akin to SCARD in Redis). It performs a read-only operation with no side effects, modifications, or deletions. Severity is low as it only exposes a numeric count value.
From the tool's definition Get number of members in set... Returns: Number of members or error message
Attacks that exploit this kind of access
The rule that runs set_cardinality 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 set_cardinality, this is the rule to start with:
set_cardinality is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect AWS, apply this rule, and every set_cardinality call is checked against it from then on.
Questions about set_cardinality
Get number of members in set. Args: key: The name of the key Returns: Number of members or error message. It is categorised as a Read tool in the AWS MCP Server, which means it retrieves data without modifying state.
Register the AWS MCP server in PolicyLayer and add a rule for set_cardinality: 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.
set_cardinality is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the set_cardinality 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.
Set action: deny in the PolicyLayer policy for set_cardinality. 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.
set_cardinality 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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