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

# Functions

> Deploy and run serverless functions in Cognite Data Fusion (CDF).

The functions area of the API covers two related families: **Functions** (classic serverless Python functions) and **Function Apps** (function applications identified by external IDs, with calls, logs, and related operations).

## Function Apps vs Functions APIs

* **Functions** (`/functions/...`) — Deploy and manage **function** definitions, **schedules**, and **calls** using the traditional Functions resource model (function IDs, schedules, call history, and logs).
* **Function Apps** (`/function-apps/...`) — Manage **function applications** by **external ID**, including **calls**, **response** and **logs** for a call, and Model Context Protocol (**MCP**) operations where exposed in the API reference.

Choose the **Functions** endpoints when you work with standard CDF functions and schedules. Choose **Function Apps** when you integrate with the **Function Apps** paths and external ID–based application flows described in the API reference.

## APIs in this group

* [Functions](/api-reference/concepts/20230101/functions) — Deploy and manage serverless Python functions
* [Function calls](/api-reference/concepts/20230101/function-calls) — Invoke functions and track execution
* [Function schedules](/api-reference/concepts/20230101/function-schedules) — Schedule recurring function invocations
* **Function Apps** — List and manage function applications and their calls (`/function-apps/...`) as documented in the API reference for your **calendar version**