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

# Overview

Extensions connect agents to messaging channels or adjust context, tool results, and response checks during a run. Choose a guide by task; moderation configuration is covered in Security

| Extension | Purpose | Prerequisites |
| - | - | - |
| [Feishu messaging](/productions/veadk/preview/en/components/extensions/feishu-channel) | Receive bot messages, run them through Runner, and reply | Bot credentials, message events, read and send permissions |
| [Harness](/productions/veadk/preview/en/components/extensions/harness) | In-process enhancement plugins or a managed Sidecar | Model configuration; Sidecar also requires a runtime |

[Content safety](/productions/veadk/preview/en/components/security/content-safety) uses callbacks to call an external moderation service. [Harness deployment](/productions/veadk/preview/en/deploy/harness) covers creating and deploying a standalone runtime, which has a different setup from in-process plugins