list_namespaces

List all namespaces across all S3 table buckets. Permissions: You must have the s3tables:ListNamespaces permission to use this operation.

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-namespaces.md

WHAT IT DOES

What list_namespaces does on AWS

AI agents call list_namespaces 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_namespaces is rated Low

This is a query operation that retrieves information about S3 table bucket namespaces without side effects. However, severity is medium (not low) because listing all namespaces across all S3 buckets could expose sensitive organizational structure and bucket names to an AI agent, potentially enabling reconnaissance for further attacks.

From the tool's definition Tool name 'list_namespaces' and description 'List all namespaces across all S3 table buckets' indicate retrieval of data without modification. The permission requirement 's3tables:ListNamespaces' confirms read-only access to bucket metadata.

Attacks that exploit this kind of access

RECOMMENDED RULE

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

list_namespaces Allowed

list_namespaces 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_namespaces": {}
  }
}

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_namespaces call is checked against it from then on.

FAQ

Questions about list_namespaces

What does the list_namespaces tool do? +

List all namespaces across all S3 table buckets. Permissions: You must have the s3tables:ListNamespaces permission to use this operation. 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_namespaces? +

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

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

Can I rate-limit list_namespaces? +

Yes. Add a rate_limit block to the list_namespaces 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_namespaces completely? +

Set action: deny in the PolicyLayer policy for list_namespaces. 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_namespaces? +

list_namespaces 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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