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

# Tolerant reader

> An integration design pattern that absorbs Lerian API changes without breaking your client code.

As our public API evolves to meet new requirements and enhance functionality, integrators, and clients need to adapt seamlessly. A key pattern supporting resilience to such changes is the **Tolerant Reader**.

By adopting the Tolerant Reader pattern, integrations can better handle new information without frequent updates. This approach reduces maintenance needs and enhances resilience, creating a smoother integration experience.

## What is a tolerant reader?

***

The Tolerant Reader pattern is an integration design approach where a client consuming data is built to handle potential changes—such as added fields or minor structure modifications—gracefully. This pattern promotes forward compatibility, reducing the need for immediate updates whenever the data or service evolves.

## Real-world scenario

***

Consider a request to `GET /organizations/{organization_id}`. Initially, the response might be:

<CodeGroup>
  ```jsonon JSON theme={null}
  {
      "id": "cc15194a-6bc9-4ebb-b15d-43411a54ba4b",
      "parentOrganizationId": null,
      "legalName": "Empresa Teste Ltda",
      "legalDocument": "86820799000188",
      "metadata": null,
      "status": {
          "code": "ACTIVE",
          "description": null
      },
      "createdAt": "2024-02-08T16:59:31+0300",
      "updatedAt": "2024-02-08T16:59:31+0300",
      "deletedAt": null
  }
  ```
</CodeGroup>

Later, fields like `doingBusinessAs` and `address` may be added:

<CodeGroup>
  ```jsonon JSON expandable theme={null}
  {
      "id": "cc15194a-6bc9-4ebb-b15d-43411a54ba4b",
      "parentOrganizationId": null,
      "legalName": "Empresa Teste Ltda",
      "doingBusinessAs": "Empresa Teste",
      "legalDocument": "86820799000188",
      "address": {
          "line1": "Rua Botucatu, 10",
          "line2": "Casa B",
          "zipCode": "04023060",
          "city": "São Paulo",
          "state": "SP",
          "country": "BR"
      },
      "metadata": null,
      "status": {
          "code": "ACTIVE",
          "description": null
      },
      "createdAt": "2024-02-08T16:59:31+0300",
      "updatedAt": "2024-02-08T16:59:31+0300",
      "deletedAt": null
  }
  ```
</CodeGroup>

A client that follows the Tolerant Reader pattern would handle the additional fields without issue, ensuring continued functionality.

## Implementing a tolerant reader

***

Below is an example Python code snippet that processes additional fields gracefully, accounting for changes in the payload.

<CodeGroup>
  ```python Python expandable theme={null}
  def fetch_organization_info(organization_id):
      response = requests.get(f"{host}/organization/{organization_id}")
      org_info = response.json()

      # Fetch required fields
      legal_name = org_info.get("legalName", "Unknown")
      legal_document = org_info.get("legalDocument", "No document provided")

      # Handle optional fields
      doing_business_as = org_info.get("doingBusinessAs")

      # Nested address structure
      address_info = org_info.get("address", {})
      line1 = address_info.get("line1", "Address not provided")
      city = address_info.get("city", "City not provided")
      state = address_info.get("state", "State not provided")
      country = address_info.get("country", "Country not provided")

      # Display information
      print(f"Legal Name: {legal_name}, Legal Document: {legal_document}")
      print(f"Doing Business As: {doing_business_as}")
      print(f"Address: {line1}, {city}, {state}, {country}")

  # Example usage
  fetch_organization_info("cc15194a-6bc9-4ebb-b15d-43411a54ba4b")
  ```
</CodeGroup>

In this example, `get` methods are used to safely access values. This allows for flexibility if new fields, such as `phoneNumber`, are introduced, as the code remains functional even if a field is absent.