HOI4 Agent Tools

HOI4 Agent Tools is an MCP server for coding agents to analyze Hearts of Iron IV event chains and inspect, create, or clean up focus trees, scripted GUIs, and maps. Start it in a mod folder and it works there immediately, with offline renders for review.

What it does

• Focus trees: inspect structure and references, render layouts, create trees, and reorganize existing branches.
• Scripted GUIs: trace GUI, GFX, scripted-GUI, and localisation links; render states; create or repair interface source.
• Maps: inspect provinces, states, regions, adjacency, supply, and railways; render layers; create and repair exact map data.
• Event chains: scan definitions and call sites, trace routes and state flow, lint references, render graphs, and compare revisions without editing event source.

Setup

Requires Node.js 22 or 24.

npm install --global [email protected]

Start the MCP with its working directory set to the mod you are editing. No config or per-mod registration is required: the server finds that mod automatically. Run hoi4-agent-tools-setup --init only when you want persistent discovery for several mod roots, a custom game path, or a remote deployment; see Setup.

Connect your agent

hoi4-agent-tools-setup --print-client-config

Paste the printed Codex or generic global-install entry into your MCP client, then restart it. The utility prints the correct command for the current operating system.

Tools

Tool	Purpose
hoi4.focus_inspect	Read focus trees and report structural or reference problems.
hoi4.focus_render	Render an existing focus tree or continuous palette.
hoi4.focus_rewrite	Create or update a focus tree.
hoi4.gui_inspect	Read a scripted GUI and its linked assets and logic.
hoi4.gui_render	Render GUI states and resolutions offline.
hoi4.gui_rewrite	Create or update a GUI source package.
hoi4.map_inspect	Read map, state, province, region, supply, and railway data.
hoi4.map_render	Render map layers and overlays.
hoi4.map_rewrite	Create or update map data from an ordered list of exact changes.
hoi4.event_inspect	Scan, trace, explain, lint, or assess event chains and their state flow.
hoi4.event_render	Render source-linked event routes, options, timing, state, scope, and unresolved edges.
hoi4.event_compare	Compare event-chain topology and diagnostics between revisions.

Large outputs are linked hoi4-agent:// resources. For resources over 1 MiB, follow the continuationUri returned in _meta until it is null; clients may also request byte ranges with ?offset=<bytes>&length=<bytes>.

Coexistence with agent workflows

HOI4 Agent Tools provides HOI4 domain operations; it does not register MCP prompts, replace repository instructions such as AGENTS.md, manage skills or plans, or start subagents. The coding agent decides when to call it as part of its existing workflow.

Connecting and listing tools does not scan mod source. Compact tool schemas and linked resources keep large diagnostics, renders, and diffs out of the agent's working context until needed. The event tools are read-only; only hoi4.*_rewrite calls edit mod source.

Create or clean content

Ask your agent in normal task language. A typical workflow is inspect, render, rewrite, then inspect the result.

• Focus trees: "Create a complete national focus tree for this route specification," or "Compact this existing tree into a balanced, readable layout." Existing trees can use a plan-free compact reflow; new trees use a complete plan. See Focus trees.
• Scripted GUIs: "Create a scripted GUI for this mechanic," or "Render this window at common resolutions and fix clipping, missing assets, and click-region conflicts." See Scripted GUIs.
• Maps: "Create a state from these exact provinces," or "Inspect this state and split these provinces while keeping supply and railway references valid." See Maps.
• Event chains: "Trace every route from this event and explain where its flags and variables change," or "Compare the workspace event graph with its previous revision and render the affected routes." See Event chains.

HTTP

Use stdio for local MCP clients. For shared or remote deployments, see HTTP.

Development

npm ci
npm run check

See Development. Apache-2.0 licensed. Hearts of Iron IV and Paradox Interactive are trademarks of their respective owners; this project is unaffiliated.