Cities2 MCP and Modding Toolkit

Cities2 MCP and Modding Toolkit is a local MCP server and agent skill bundle for Cities: Skylines II gameplay questions, patch notes, and mod project workflows.

It gives AI agents access to a bundled, searchable Cities: Skylines II Wiki corpus and, when the game is installed locally, the in-game encyclopedia. Agents can use those sources to answer gameplay questions, summarize patch/update information, and explain city systems with source notes. The package also includes five agent skills for game knowledge, modding, review, debugging, and release readiness, plus local MCP workflow tools for scaffolding, inspecting, building, and packaging CS2 mod projects inside trusted workspaces.

The plugin is in active development. Package checks, direct MCP smoke tests, and selected client workflows are covered in the repository test suite and eval reports, but client plugin behavior can vary by host and version. See the known issues and eval reports for the latest verification notes.

Quick install

Choose your client: Claude Code | Claude desktop | Codex CLI | Codex app | Google Antigravity

See INSTALL.md for full installation details, direct MCP config, workspace setup, build prerequisites, and troubleshooting.

What it can do

Search game and modding information

The MCP server includes a prepared text corpus from the Cities: Skylines II Wiki. An AI assistant can:

• search the wiki
• retrieve full pages, page-level references, and code-oriented snippets for game systems, patch notes, and modding topics
• answer questions about game mechanics, recent updates, and how city systems affect your save

Search the local game encyclopedia

When Cities: Skylines II is installed locally, the MCP server reads the game encyclopedia from the installed game files. This source is enabled by default when the server can find Cities2_Data/Content/Game/Locale.cok.

The extracted encyclopedia index is cached locally on the user's machine and rebuilt only when the source game file, detected Steam build id, locale, or extractor version changes. Extracted game text is not committed to this repository, shipped in releases, or part of the redistributed wiki corpus.

Help with mod project workflows

The server also includes local workflow tools for CS2 mod projects. An AI assistant can:

• scaffold C# code, UI, or hybrid mod project templates
• write files inside configured workspaces
• list project trees
• run project builds and analyzers
• package project output

These tools are meant for local development workflows. Claude, Codex, and Antigravity can use them to write and run trusted workspace code during builds, so configure workspaces deliberately and use manual playtesting before treating any mod as ready to share.

Agent skills

• cities2-knowledge: answers gameplay, city-system, and player-facing patch/update questions.
• cities2-modding: handles general modding questions and local mod project workflows.
• cities2-mod-review: reviews CS2 mods for safety, maintainability, user value, packaging hygiene, and verification gaps.
• cities2-mod-debugging: helps debug CS2 mod build, packaging, runtime, log, UI debugger, and in-game behavior issues.
• cities2-mod-release: checks whether a mod is ready to share.

The modding quality skills use documented CS2 best practices and negative constraints as defaults, and they do not present a mod as ready to share until it has been locally playtested.

Privacy

The MCP server runs locally and does not collect telemetry. See PRIVACY.md for details.

Licensing

The MCP server code is licensed under the MIT License. The included cities2_mcp/data corpus is licensed under Creative Commons Attribution-ShareAlike 3.0; source attribution and transformation notes are in cities2_mcp/data/ATTRIBUTION.md.

This project is not developed by, endorsed by, reviewed by, or approved by Paradox Interactive, Iceflake Studios, Colossal Order, Paradox Wikis, or any related company. Cities: Skylines II and related names are used referentially.