unreal-api-mcp

MCP server that gives AI agents accurate Unreal Engine C++ API documentation. Saves tokens, context, and time — prevents hallucinated signatures, wrong #include paths, and deprecated API usage.

Works with Claude Code, Cursor, Windsurf, or any MCP-compatible AI tool. No Unreal Engine installation required. Check the supported versions. New versions are detected and built automatically every week.

Quick Start

Add to your MCP config (.mcp.json, mcp.json, or your tool's MCP settings), setting UNREAL_VERSION to match your project:

{
  "mcpServers": {
    "unreal-api": {
      "command": "uvx",
      "args": ["unreal-api-mcp"],
      "env": {
        "UNREAL_VERSION": "5.5"
      }
    }
  }
}

Set this to match your project's UE version. See supported versions for all available databases.

On first run the server downloads the correct database to ~/.unreal-api-mcp/. Patch versions (e.g. "5.7.3") fall back to the major.minor database (e.g. "5.7") if a patch-specific one isn't available.

How It Works

1. Version detection. The server figures out which UE version to serve:

Set one of these to match your project. Without either, the server defaults to UE 5.7.

2. Database download. If the database for that version isn't cached locally, it downloads from GitHub (one time). For patch versions, falls back to the major.minor database if needed. Also checks for updates on startup.

3. Serve. All tool calls query the version-specific SQLite database. Exact lookups return in <1ms, searches in <5ms.

Each version has its own database with the correct signatures, deprecation warnings, and member lists for that release.

Tools

Coverage

All Engine Runtime, Editor, Developer modules, plus built-in plugins (Enhanced Input, Gameplay Abilities, Common UI, Niagara, Chaos, and hundreds more).

Includes Blueprint graph internals: 158 UK2Node subclasses, UEdGraphSchema_K2, BlueprintGraph, KismetCompiler, and GraphEditor modules (1,120+ entries). If you're writing custom K2 nodes or editor tooling, it's indexed.

See the full list of supported versions and databases on the db-v1 release page. New versions are detected and built automatically every Monday via CI.

Record breakdown (UE 5.7):

Does not cover third-party plugins or marketplace assets. For those, rely on project source.

Benchmarks

In a 10-step character movement development workflow, MCP consistently uses far fewer tokens than agents working with grep and file reads:

The gap holds across every question type. MCP wins on simple include lookups and complex class references alike:

Even in a realistic hybrid workflow where MCP results are followed up with targeted file reads, it still uses significantly fewer tokens than a skilled agent working without MCP:

"Without MCP" estimates assume full or partial file reads. A skilled agent with good tooling may use fewer tokens than shown. What MCP guarantees is a correct, structured answer in one call every time.

Per-question breakdown

Measured on UE 5.7 database (114,724 records), 50 iterations per query:

Ranking uses BM25 with tuned column weights (member name 10x, class name 5x) plus core module boosting to ensure AActor::GetActorLocation ranks above niche plugin APIs.

CLAUDE.md Snippet

Add this to your project's CLAUDE.md (or equivalent instructions file). This step is important. Without it, the AI has the tools but won't know when to reach for them.

## Unreal Engine API Lookup (unreal-api MCP)

Use the `unreal-api` MCP tools to verify UE C++ API usage instead of guessing. **Do not hallucinate signatures or #include paths.**

| When | Tool | Example |
|------|------|---------|
| Unsure about a function's parameters or return type | `get_function_signature` | `get_function_signature("AActor::GetActorLocation")` |
| Need the `#include` for a type | `get_include_path` | `get_include_path("ACharacter")` |
| Want to see all members on a class | `get_class_reference` | `get_class_reference("UCharacterMovementComponent")` |
| Searching for an API by keyword | `search_unreal_api` | `search_unreal_api("spawn actor")` |
| Checking if an API is deprecated | `get_deprecation_warnings` | `get_deprecation_warnings("K2_AttachRootComponentTo")` |
| Writing custom K2 nodes or editor tools | `get_class_reference` | `get_class_reference("UK2Node_SpawnActorFromClass")`, `get_class_reference("UEdGraphSchema_K2")` |

**Rules:**
- Before writing a UE API call you haven't used in this conversation, verify the signature with `get_function_signature`
- Before adding a `#include`, verify with `get_include_path` if unsure
- Covers: all Engine Runtime/Editor modules, built-in plugins (Enhanced Input, GAS, CommonUI, Niagara, etc.), Blueprint graph internals (UK2Node subclasses, EdGraphSchema, BlueprintGraph, KismetCompiler)
- Does NOT cover: third-party plugins or marketplace assets

Setup Details

Instead of setting UNREAL_VERSION, you can point to your Unreal project. The server reads the EngineAssociation field from your .uproject file:

{
  "mcpServers": {
    "unreal-api": {
      "command": "uvx",
      "args": ["unreal-api-mcp"],
      "env": {
        "UNREAL_PROJECT_PATH": "F:/Unreal Projects/MyProject"
      }
    }
  }
}

Using pip install:

pip install unreal-api-mcp

{
  "mcpServers": {
    "unreal-api": {
      "command": "unreal-api-mcp",
      "args": [],
      "env": {
        "UNREAL_VERSION": "5.5"
      }
    }
  }
}

If you want to build a database from your own Unreal Engine installation instead of downloading:

# Build for a specific version
python -m unreal_api_mcp.ingest --unreal-version 5.6 --unreal-install "H:/UE_5.6"
python -m unreal_api_mcp.ingest --unreal-version 5.5 --unreal-install "H:/UE_5.5"

Databases are written to ~/.unreal-api-mcp/unreal_docs_{version}.db by default.

unreal-api-mcp/
├── src/unreal_api_mcp/
│   ├── server.py          # MCP server (5 tools)
│   ├── db.py              # SQLite + FTS5 database layer
│   ├── version.py         # Version detection + DB download
│   ├── header_parser.py   # Parse Unreal C++ headers (UCLASS, UFUNCTION, etc.)
│   ├── unreal_paths.py    # Locate UE installs + discover modules
│   └── ingest.py          # CLI ingestion pipeline
└── pyproject.toml

Databases are stored in ~/.unreal-api-mcp/ (downloaded on first run).

Troubleshooting

See Also

unity-api-mcp — Same concept for Unity (C#). Covers Unity 2022, 2023, and Unity 6.

Contact

Need a custom MCP server for your engine or framework? I build MCP tools that cut token waste and prevent hallucinations for AI-assisted game development. If you want something similar for your team's stack, reach out.

fuatcankoseoglu@gmail.com

License

PolyForm Noncommercial 1.0.0

Free to use, fork, modify, and share for any personal or non-commercial purpose. Commercial use requires permission.