list_canaries

ServerAWS
CategoryRead

WHAT IT DOES

What list_canaries does on AWS

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

THE RISK

Low Risk

Why list_canaries needs a policy

This tool retrieves monitoring configuration data from AWS CloudWatch Synthetics without modifying, executing, or deleting anything. It is purely informational, used to discover canaries before analysis. The blast radius of misuse is limited to information disclosure about monitoring infrastructure.

From the tool's definition Tool name 'list_canaries' and description 'List all CloudWatch Synthetics canaries in the account' with return value 'Formatted list of all canaries with their current status and configuration' indicates a query/list operation with no side effects.

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

POLICY

How to control list_canaries

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

policy.json

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

list_canaries is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

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

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EXPLORE

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FAQ

Questions about list_canaries

What does the list_canaries tool do? +

List all CloudWatch Synthetics canaries in the account. Use this tool to discover canaries before analyzing them with analyze_canary_failures(). Returns canary names, status, schedule, runtime version, and last run state. Args: region: AWS region to query (defaults to configured region). max_results: Maximum number of canaries to display (default: 20, max: 200). Returns: Formatted list of all canaries with their current status and configuration. 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_canaries? +

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

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

Can I rate-limit list_canaries? +

Yes. Add a rate_limit block to the list_canaries 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_canaries completely? +

Set action: deny in the PolicyLayer policy for list_canaries. 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_canaries? +

list_canaries 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.

Enforce policy on every AWS tool call.

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