Extensions
Use built-in tools, install registry extensions, and add custom MCP servers in AgentOne.
AgentOne uses the term extensions for two distinct things that both add capabilities to the AI:
- Built-in tools - a curated set of tools that ship with the app (file operations, web search, command execution, and more).
- MCP servers - external Model Context Protocol servers you install from the registry or add yourself.
Both types are managed from Settings -> Extensions.
Extensions are in beta
The app labels extensions as beta. Some behavior may still change between releases.
Topics
Built-in Tools
Enable built-in tools and configure how each one behaves.
Extension Registry
Search, filter, and browse installable extensions from the registry.
Install Extensions
Install registry extensions and review their configuration before enabling.
Custom MCP Servers
Add your own STDIO or HTTP MCP servers.
Approval & Auth
Control per-tool approvals and connect HTTP extensions that require sign-in.
Dangling Extensions
Find and remove extensions that no longer map to registry entries.
How Extensions Appear in a Chat
When a model that supports tools is selected, enabled extensions offer their tools to the model during the conversation. The model can then call those tools as part of its response - for example, searching the web, reading a file, or running a shell command.
Tool calls appear inline in the chat as collapsible activity items so you can see exactly what the model did. If approval is required for a tool, AgentOne pauses and asks before running it.
MCP Apps (Beta)
Extensions that support MCP Apps can render interactive interfaces directly in a chat. An app may appear:
- inline with the extension's tool activity
- in an Expanded extension view
- in a picture-in-picture window
Expanded and picture-in-picture views can be closed to return to the conversation. AgentOne passes the current light or dark theme, locale, platform, available display modes, and container size to compatible apps so they can fit the desktop UI. MCP Apps run in a sandboxed frame.
Related Guides
For specific real-world MCP server examples, see the Custom Extensions guides which walk through installing Smithery, Canva, and filesystem servers step by step.