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

# API Fundamentals Overview

> Comprehensive guide to Telnyx API fundamentals including authentication, protocols, webhooks, and best practices.

RESTful HTTP endpoints that consume and return JSON. Requires API token authentication for most endpoints.

## API V2 Endpoint

`https://api.telnyx.com/v2`

## S3 Compatible Endpoints

* `us-central-1.telnyxcloudstorage.com`
* `us-east-1.telnyxcloudstorage.com`
* `us-west-1.telnyxcloudstorage.com`

See [Cloud Storage API endpoints](/docs/cloud-storage/api-endpoints)

## Legacy Endpoints

<Callout type="warning">
  No documentation exists for these endpoints. All documentation under /development pertains to V2 API.
</Callout>

### V1 HTTP

* `https://api.telnyx.com/origination`
* `https://api.telnyx.com/termination`
* `https://api.telnyx.com/messaging`
* `https://api.telnyx.com/reporting`
* `https://api.telnyx.com/security`
* `https://api.telnyx.com/account`
* `https://api.telnyx.com/caller-information`
* `https://api.telnyx.com/LRN`
* `https://api.telnyx.com/LRNLookup`
* `https://sms.telnyx.com/messages`

### DNS ENUM

* `api.telnyx.com`
* `lrnlookup.telnyx.com`

### XML UDP

* `lrnlookup.telnyx.com`

## Core Concepts

### Authentication & Security

Learn how to authenticate with Telnyx APIs and secure your applications.

* [API Authentication](/development/api-fundamentals/authentication/index) - API keys, tokens, and authentication methods
* [Request & Response Handling](/development/api-fundamentals/request-response/index) - HTTP patterns and best practices

### Reliability & Performance

Understand how to build robust applications that handle errors gracefully.

* [Rate Limiting](/development/api-fundamentals/reliability/rate-limiting) - Understanding and handling API rate limits
* [Error Handling & Retries](/development/api-fundamentals/reliability/command-retries) - Retry patterns and error handling strategies

### Data Standards

Follow Telnyx conventions for data formatting and API interactions.

* [Parameters & Field Names](/development/api-fundamentals/data-standards/parameters-fields) - Naming conventions and data formats

### Real-time Communications

Implement real-time features using webhooks and event-driven architecture.

* [Webhook Fundamentals](/development/api-fundamentals/webhooks/receiving-webhooks) - Understanding and implementing webhooks