Runs an on-demand evaluation for the specified Config rules against the last known configuration state of the resources. Use StartConfigRulesEvaluation when you want to test that a rule you updated is working as expected. StartConfigRulesEvaluation does not re-record the latest configuration state for your resources. It re-runs an evaluation against the last known state of your resources.

You can specify up to 25 Config rules per request.

An existing StartConfigRulesEvaluation call for the specified rules must complete before you can call the API again. If you chose to have Config stream to an Amazon SNS topic, you will receive a ConfigRuleEvaluationStarted notification when the evaluation starts.

You don't need to call the StartConfigRulesEvaluation API to run an evaluation for a new rule. When you create a rule, Config evaluates your resources against the rule automatically.

The StartConfigRulesEvaluation API is useful if you want to run on-demand evaluations, such as the following example:

1. You have a custom rule that evaluates your IAM resources every 24 hours.
2. You update your Lambda function to add additional conditions to your rule.
3. Instead of waiting for the next periodic evaluation, you call the StartConfigRulesEvaluation API.
4. Config invokes your Lambda function and evaluates your IAM resources.
5. Your custom rule will still run periodic evaluations every 24 hours.