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

# Integration Principles

This section outlines key principles for designing and developing Pleo accounting
integrations. These principles ensure integrations are efficient, scalable,
maintainable, and meet user expectations and business needs.

### Integration Scope

* All integrations must implement at least [**Level 2 functionality**](/docs/current/getting-started/accounting-integrations-overview#integration-levels), although
  **Level 4** is recommended for full automation and user experience.

### Minimum States

* Retain state only for:
  * Authentication (e.g., API keys, OAuth 2.0 tokens)
  * Configuration parameters (user-provided settings required to run the integration)
* Avoid storing any data already stored in Pleo or the target system, unless
  unavoidable for implementing integration functionality.
* The target ERP/Accounting System is the primary source of truth for mapping
  entities and codes.
* Temporary caching is acceptable to improve the user experience during setup
  (e.g., populating dropdown selections).

### Self-Service Setup

* Integrations should allow users to configure and activate them independently
  through a self-service process.

### Resources Provided by Pleo

* All Pleo resources are available via this Developer Portal for reference and
  implementation guidance.

### API Rate Limit

* Integrations should be designed to avoid exceeding the API rate limits of
  Pleo and target systems, taking into account batch processing, retries, and
  any automated synchronisation. Each [API Reference](/reference/api-introduction) section has their own API Rate limits outlined.