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

# Introduction

Welcome to the documentation for the **Terrafai Document Extraction API**.

The Terrafai API allows you to extract structured data from unstructured documents such as invoices, receipts, bank statements, and other business documents. Using natural-language templates and intelligent document classification, the API converts documents into clean, machine-readable output that can be integrated directly into your systems.

This documentation is intended for developers and technical teams who want to automate document processing using the Terrafai platform.

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## How the Terrafai API Works

At a high level, document extraction with Terrafai follows a simple flow:

1. **Define what data you want** using templates
2. **Optionally classify documents** using filters
3. **Submit documents for extraction**
4. **Retrieve structured results**

The sections below introduce the key concepts you’ll encounter throughout the guides.

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## Core Concepts

### Templates

Templates define **what information should be extracted** from a document and **how the output should be structured**.

A template consists of:

* A set of fields written in natural language
* Data types that control how values are parsed and formatted
* Optional rules that transform or normalize extracted data

Templates are required for extraction unless you are using filters to automatically select a template.

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### Filters

Filters allow you to **classify, route, or skip documents before extraction**.

They are designed for workflows where:

* Multiple document types are submitted through the same integration
* Different templates should be applied automatically
* Irrelevant or unsupported documents should be ignored

When using filters, the system evaluates each document and decides:

* Whether it should be extracted
* Which template should be applied

This helps reduce manual routing and avoid unnecessary consumption.

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### Extraction Modes

The API supports two extraction modes:

* **Synchronous extraction**\
  Returns results in a single request–response cycle. Best for small documents and real-time use cases.
* **Asynchronous extraction**\
  Processes documents in the background and returns a job identifier. Best for large documents, batch processing, or long-running extractions.

Both modes use the same request structure and extraction options.