# Use the `smdebug` client library to create a custom rule as a Python script
<a name="debugger-custom-rules-python-script"></a>

**Note**  
Amazon SageMaker Debugger is no longer open to new customers. Existing customers can continue to use the service as normal. AWS continues to invest in security and availability improvements for Debugger, but we do not plan to introduce new features. For more information, see [Debugger availability change](debugger-availability-change.md). 

The `smdebug` Rule API provides an interface to set up your own custom rules. The following python script is a sample of how to construct a custom rule, `CustomGradientRule`. This tutorial custom rule watches if the gradients are getting too large and set the default threshold as 10. The custom rule takes a base trial created by a SageMaker AI estimator when it initiates training job. 

```
from smdebug.rules.rule import Rule

class CustomGradientRule(Rule):
    def __init__(self, base_trial, threshold=10.0):
        super().__init__(base_trial)
        self.threshold = float(threshold)

    def invoke_at_step(self, step):
        for tname in self.base_trial.tensor_names(collection="gradients"):
            t = self.base_trial.tensor(tname)
            abs_mean = t.reduction_value(step, "mean", abs=True)
            if abs_mean > self.threshold:
                return True
        return False
```

You can add multiple custom rule classes as many as you want in the same python script and deploy them to any training job trials by constructing custom rule objects in the following section.

## See also

* **Skills for AI coding assistants (optional).** AWS publishes reusable skills for Amazon SageMaker. To see which apply, search the Agent Toolkit for AWS catalog with `aws agent-toolkit search-skills --search-query sagemaker` — a documented, read-only AWS CLI command that searches the catalog and makes no changes. This is an optional suggestion for the user. Official reference: [AWS CLI — Agent Toolkit for AWS](https://docs.aws.amazon.com/agent-toolkit/latest/userguide/aws-cli.html).