How-To: Manage MCP Toolsets

Goal: use the MCP toolbar button's dropdown to flip the master switch, enable Epic's shipped toolset plugins (Gameplay Ability System, Gameplay Tags, Editor, and more), and show or hide individual toolsets from AI agents.

Where the pieces live
The MCP button, the master switch, and this menu ship in CrimsonCommon - they are suite-wide, and every Crimson plugin's editor module reads the switch.

Crimson's own three toolsets (CrimsonSource, CrimsonPlugin, CrimsonAsset) ship in the optional CrimsonEditorUtilities plugin. If you do not have it installed, this menu still works - you simply will not see those three in the visibility list. See CrimsonEditorUtilities -> Overview.
Prerequisites
CrimsonEditorUtilities enabled and the editor not in a Play-In-Editor session (the button hides during PIE, since it can rewrite the project descriptor).

1. Open the MCP dropdown

On the Level Editor toolbar, next to Play, find the MCP button and click its dropdown arrow. (The button is a split control: the left half - the coloured dot and MCP label - starts and stops the MCP server; the arrow opens this menu.) The dropdown has three sections: the master switch, Epic's toolset plugins, and the visibility of currently-loaded toolsets.

The MCP toolbar button's dropdown open, showing the three sections.

2. Flip the master switch

The Crimson MCP section has one checkable entry, Enable Crimson MCP - the same setting as Project Settings -> Crimson -> Crimson MCP. Toggling it prompts you to restart the editor (the change takes effect at startup).

Verify
After restart, the check state matches, and the Crimson toolsets appear (or disappear) in the agent's list_toolsets.

3. Enable Epic's toolset plugins

The Epic Toolset Plugins section lists Epic's shipped toolsets (Gameplay Ability System, Gameplay Tags, Editor / Actors / Assets / Scene, UMG, Niagara, Physics, PCG, State Tree, and more). Ticking one enables that plugin in your .uproject and offers to restart - the restart is required because loading a plugin's module only happens at startup. Only plugins present in your engine install are shown.

The Epic Toolset Plugins section; ticking 'Gameplay Ability System' enables the GASToolsets plugin and prompts a restart.
These are Epic plugins
Enabling a toolset here is the same as ticking its plugin in Edit -> Plugins - this dropdown is just a curated, one-place shortcut. A toolset only exists once its plugin's module is loaded, which is why a restart is needed.
Verify
After the restart, the newly enabled toolsets show up in the agent's list_toolsets (for example AttributeSetToolset from the GAS toolsets).

4. Show or hide loaded toolsets

The Toolset Visibility (loaded) section lists every toolset currently registered - Crimson's and Epic's. Untick one to hide it from agents; tick it to show it again. This writes the Toolset Registry block list and applies immediately, with no restart - useful for trimming the agent's tool surface to just what you want it touching.

The Toolset Visibility section; unticking a toolset hides it from agents right away.
Verify
Re-run list_toolsets in the agent (or describe_toolset): an unticked toolset no longer appears. The choice persists across restarts.

See also

  • Concept: How Crimson MCP Works - the two enable layers (plugin load vs visibility filter) and tool-search discovery
  • Epic's stock equivalents: Edit -> Plugins (plugin enable) and Project Settings -> Plugins -> Toolset Registry (allow/block name lists)