# API Reference

**Interfaces for querying your Lynk semantic layer.**

This section documents the query interfaces exposed by Lynk — how to write queries against your semantic layer and how to call Lynk programmatically.

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## What's in this section

| Page                                                           | What it covers                                                                                                                                 |
| -------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------- |
| [Lynk SQL](https://docs.getlynk.ai/api-reference/api/lynk-sql) | The SQL dialect the agent uses internally and you use when writing evaluation test cases — `entity()`, `metric()`, joins, supported statements |
| [REST API](https://docs.getlynk.ai/api-reference/api/rest-api) | HTTP endpoints for querying the semantic layer programmatically                                                                                |

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**Where to go next:**

* Need to understand how entities and metrics are defined? → [Concepts](https://docs.getlynk.ai/concepts/concepts)
* Writing evaluation test cases that use Lynk SQL? → [Evaluations YAML](https://docs.getlynk.ai/file-types-reference/file-types/evaluations-yaml)