Cities2 MCP Server

Cities2-MCP

Cities2-MCP — a local MCP server for Cities: Skylines II game knowledge and modding tools.

It gives AI assistants access to a prepared local corpus of Cities: Skylines II Wiki text, plus tools for creating, inspecting, building, and packaging CS2 mod projects.

What It Can Do

Search Game And Modding Information

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

• search the bundled wiki corpus
• fetch full pages by page id
• retrieve reference-style snippets for game systems and modding topics
• answer questions without browsing the live wiki during your session

This is useful for questions about game mechanics, modding APIs, toolchain setup, project structure, localization, UI mods, and related CS2 development topics.

Search The Local Game Encyclopedia

When Cities: Skylines II is installed locally, Cities2-MCP also tries to read the in-game Encyclopedia from the user's own game files. This source is enabled by default when the server can find Cities2_Data/Content/Game/Locale.cok, especially for standard Steam installs.

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.

If the game install is not found automatically, set CITIES2_GAME_DIR to the Cities: Skylines II install directory or CITIES2_LOCALE_COK to the full Locale.cok path.

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
• dry-run launching Cities: Skylines II with selected flags

These tools are meant for local development workflows. They can write files and run commands, so configure workspaces deliberately.

Use Slash Commands

Cities2-MCP ships two slash-command skills that teach compatible agents how to query and interpret the MCP sources effectively:

• cities2-knowledge answers gameplay, city-system, and player-facing patch/update questions from both the bundled wiki corpus and the local game Encyclopedia.
• cities2-modding answers modding questions and guides local mod project workflows.

These skills are stored in skills/. Install or copy them into your agent's skill directory if your client supports Agent Skills. They are the recommended way to get natural answers to questions like "how do I grow office demand?" or "what changed in the latest patch?" because they tell the agent to use keyword queries, fetch full pages or entries, compare source authority, synthesize an answer, and include compact source notes naming the Game Encyclopedia entries and linked wiki pages used.

Licensing

The MCP server code is licensed under the MIT License. The internal retrieval layer includes code originally split out as wiki-mcp; its MIT notice is preserved in THIRD_PARTY_NOTICES.md. 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.

Privacy Policy

Cities2-MCP runs locally on the user's machine. It does not collect telemetry, send usage data to mayor-modder, or require an account.

The server reads the bundled wiki corpus from the installed package. When available, it can read the user's local Cities: Skylines II game files to build a local in-game Encyclopedia cache. If workflow tools are enabled with --workspace, it can read and write files only inside the configured trusted workspace paths. Build, package, and launch tools may run local development commands on the user's machine when explicitly invoked by the connected agent.

Cities2-MCP does not share data with third parties. Local cache files remain on the user's machine. Users can remove the package, MCP client configuration, and local Encyclopedia cache at any time. Privacy or security issues can be reported through the GitHub issue tracker.

Quick Install

The packaged server includes the bundled wiki corpus and can be launched by MCP clients through uvx:

{
  "mcpServers": {
    "cities2-mcp": {
      "command": "uvx",
      "args": [
        "cities2-mcp",
        "--workspace",
        "/absolute/path/to/trusted/mod/workspace"
      ]
    }
  }
}

Omit --workspace if you only want wiki and local Encyclopedia search. Add one or more --workspace entries when you want the project workflow tools to write, analyze, build, or package local mod projects.

To install the bundled slash-command skills for Codex and Claude Code, run:

uvx cities2-mcp install-agent-assets

The plain MCP install command only connects the server. This helper installs the two user-facing agent assets too: cities2-knowledge and cities2-modding. For Claude Code it also writes /cities2-knowledge and /cities2-modding command files under ~/.claude/commands.

Prerequisites

Clone the repository:

git clone https://github.com/mayor-modder/Cities2-MCP.git

The wiki retrieval code is included directly under cities2_mcp/retrieval, so no submodule setup is required.

Optional mod build/package workflows need the Cities: Skylines II modding toolchain, dotnet, and a .NET 6 runtime. Check with:

dotnet --list-runtimes

Look for Microsoft.NETCore.App 6.. This is only required for tools that build, post-process, or package CS2 mods; wiki search and project scaffolding do not need it.

Install In Claude Desktop, Claude Code, Codex, Cursor, etc.

See INSTALL.md for step-by-step setup instructions. The install guide covers client detection, config file locations, and troubleshooting for supported platforms.

Reference config templates with placeholders are also available at:

• mcp.config.example.json for JSON clients
• INSTALL.md includes the Codex TOML shape

Anthropic Distribution

Cities2-MCP includes two Anthropic package shapes under integrations/anthropic/:

• claude-plugin/ is the Claude Code plugin. It bundles the two skills and a intentionally does not auto-configure MCP, because the simple Claude Code MCP command path depends on uvx being installed separately.
• claude-mcpb/ is the Claude Desktop MCPB source. It uses Anthropic's uv runtime support and wraps the published PyPI package for one-click local desktop-extension installs without asking users to install uvx manually.

Local PyPI MCP servers are not listed directly in Anthropic's Connectors Directory. The plugin is the path for Claude Code skill discoverability; the MCPB is the path for Claude Desktop extension testing and Connectors Directory submission.

Start MCP Server

Run from the repository root:

CITIES2_MODS_DIR="$HOME/Library/Application Support/Colossal Order/Cities Skylines II/Mods" \
python3 server/mcp_server.py \
  --workspace .

Transport is stdio with Content-Length framing. The server also accepts newline-delimited JSON for compatibility.

Repeat --workspace to allow additional project roots. Relative tool paths resolve from the first workspace. Absolute project paths must live inside one of the configured workspaces.

Included Wiki Corpus

The packaged server reads the prepared corpus from cities2_mcp/data by default. The corpus contains page metadata and JSONL indexes used by the MCP retrieval tools.

Corpus layout:

• cities2_mcp/data/LICENSE
• cities2_mcp/data/ATTRIBUTION.md
• cities2_mcp/data/manifest.json
• cities2_mcp/data/index/pages.jsonl
• cities2_mcp/data/index/chunks.jsonl

MCP Tools

Game and modding knowledge:

• search(query, limit=5)
• get_page(page_id)
• query_reference(query, limit=5)
• get_snippets(query, limit=3)
• search_encyclopedia(query, limit=5)
• get_encyclopedia_entry(entry_id)
• source_status()

Mod project workflow:

• scaffold_project(name, template, target_dir?, metadata?, options?)
• write_project_file(project_dir, relative_path, content, mode=create|replace|upsert)
• list_project_tree(project_dir, glob="**/*", include_hidden=false, max_files=2000)
• build_project(project_dir, profile=debug|release, steps?, clean=false, package=false, timeout_sec=300)
• analyze_project(project_dir, profile=auto|cities2-csharp|cities2-ui|cities2-hybrid, strict=true)
• package_project(project_dir, output_dir?, package_name?, exclude_globs?)
• launch_cities2(executable?, flags?, platform=auto|mac|windows|linux, dry_run=true)

Slash Commands

Skills live under skills/:

• skills/cities2-knowledge/SKILL.md
• skills/cities2-modding/SKILL.md

Install them into a compatible client's skill folder, or keep them in the repo as project-level guidance where supported. The skills depend on the cities2-mcp MCP server being configured. Gameplay and update answers should include compact source notes that mention the local Game Encyclopedia entries and link to the relevant CS2 Wiki pages when available.

Packaged installs can copy these assets from the wheel:

uvx cities2-mcp install-agent-assets

Use --client codex or --client claude to target one client. The installer also removes the old cities2-game-updates asset name from the target client folders so stale commands do not linger after upgrading.

Project templates are stored at:

• cities2_mcp/templates/cities2-csharp
• cities2_mcp/templates/cities2-ui
• cities2_mcp/templates/cities2-hybrid

Migration From Older Tool Names

• create_mod_project -> scaffold_project
• add_file / update_file -> write_project_file
• list_project_files -> list_project_tree
• build_mod -> build_project
• check_errors -> integrated in build_project diagnostics output
• package_mod -> package_project
• export_mod_copy -> removed; use package_project plus an external copy step if needed
• launch_game_with_flags -> launch_cities2

Smoke Test

python3 tests/smoke_mcp.py

The smoke test validates MCP initialize/list plus wiki retrieval and mod workflow tools end-to-end.

Direct CLI

python3 scripts/workbench_cli.py list-tools
python3 scripts/workbench_cli.py scaffold "My Mod" cities2-csharp
python3 scripts/workbench_cli.py analyze mods/my-mod --profile auto --strict
python3 scripts/workbench_cli.py build mods/my-mod --profile release --steps ui,dotnet