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sidebar_label: 'API conventions'
sidebar_position: 4
---

# API conventions

## Versioning

The Future Ordering API is versioned using a custom request header: `X-Api-Version: 0`. If this header is missing from a request, the API rejects the request.

## Errors

The Future Ordering API returns errors with standard HTTP status codes, including but not limited to `400`, `401`, `403`, `404`, `405`, `409`, `412`, `429`, and `500`. Each error response includes an `ErrorInfo` object with a `message` and `code` field to help you understand what went wrong.

## Rate limits

All API consumers are tied to an API subscription. Your subscription includes allowances for number of calls, requests per second, and bandwidth consumed.

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## Request size limits

The API enforces a request size limit of 100 KB as a general rule. Exceptions apply to content APIs whose purpose is to handle large amounts of data, such as image uploads.