> ## Documentation Index
> Fetch the complete documentation index at: https://docs.timeback.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Evaluating apps

> How Timeback measures app quality

<Note>This page describes product principles and review policy. These thresholds are not universal enforcement in every SDK or receiver. Check the relevant integration contract and confirm current approval requirements with the Timeback team.</Note>

Timeback operates on a simple principle: **if students are not learning, it is the system's fault.** Apps are evaluated the same way.

| Dimension | What matters |
| - | - |
| **Granularity** | One teachable unit at a time |
| **Instruction quality** | Clear explanations, worked examples, minimal noise |
| **Mastery truthfulness** | "Completed" means mastered |
| **Coverage and rigor** | Aligned to real external tests |
| **Efficiency** | Fewer hours to reach the same verified outcome |
| **Hole-filling compatibility** | Targeted remediation is possible when gaps show up |

If an app performs well on engagement but poorly on externally validated outcomes, the closed loop forces the conversation back to instruction, mastery, and signal integrity.

<CardGroup>
  <Card title="Non-negotiables" href="/beta/about-timeback/concepts/non-negotiables">
    The rules every app must follow.
  </Card>

  <Card title="Integration levels" href="/beta/build-on-timeback/integration-levels">
    Level 1 vs Level 2 requirements.
  </Card>
</CardGroup>