# Using the /trace endpoint

> All the examples provided here are from the [country package template](https://github.com/openfisca/country-template).

When you [run a simulation](input-output-data.md) on a specific situation (e.g. use the `/calculate` endpoint), you might want to understand the calculation or be surprised by its result. The `/trace` endpoint is here to help you analyse the simulation calculation step by step. 

Add page for trace endpoint
Add page for trace endpoint
