MCP Server Extension for Unity

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A plugin that extends the MCP Server built into JetBrains Rider. Adds tools for operating Unity Editor from any Coding Agents.

Features

• No per-project MCP server package required — no need to install an MCP server package into each Unity project.
• No agent configuration — if the MCP Server is already enabled in Rider, Coding Agents can use the tools immediately with no additional setup.
• No additional configuration required for cloned workspaces — if you clone a workspace with git workspace, claude --workspace, etc., you get tools that work without any additional configuration.
• Tools for Unity Editor — provides Run tests, Run editor script, Check compilation, and Play mode control.

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Requirements

• JetBrains Rider 2025.3+

[!NOTE]
Rider 2026.2 introduced a breaking change to the Rd protocol API that this plugin must compile against.
Using Rider 2026.1.x or earlier? Install v1.0.7 instead.

Provided Tools

Run tests

The run_unity_tests tool runs tests on Unity Editor through Rider's test infrastructure. Recommend filtering by assemblyNames, categoryNames, groupNames, and testNames to narrow down the tests to the scope of changes.

[!TIP]
You can also run Play Mode tests with domain reloading.

Parameters

| Name | Required | Description | |-----------------|--------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | testMode | Required | EditMode or PlayMode (case insensitive). If the includePlatforms in the assembly definition file (.asmdef) contains Editor, it is an Edit Mode test; otherwise it is a Play Mode test. | | assemblyNames | Required | Names of test assemblies to run (without .dll extension, e.g. MyFeature.Tests). Specify the name property in the assembly definition file. | | categoryNames | Optional | Names of a category to include in the run. Any test or fixture runs that have a category matching the string. | | groupNames | Optional | Same as testNames, except that it allows for Regex. This is useful for running specific fixtures or namespaces. | | testNames | Optional | The full name of the tests to match the filter. This is usually in the format FixtureName.TestName. If the test has test arguments, then include them in parentheses. |

Response

| Field | Type | Description | |---------------------|---------|----------------------------------------------------------------| | success | boolean | true if all tests passed | | passCount | number | Number of passing tests | | failCount | number | Number of failing tests | | inconclusiveCount | number | Number of inconclusive tests | | skipCount | number | Number of skipped tests | | failedTests | array | Details of failed tests (testId, output, duration) | | inconclusiveTests | array | Details of inconclusive tests (testId, output, duration) |

[!NOTE]
To save space in the context window, outputs of successful and skipped tests are not included in the response.

Error Response

| Field | Type | Description | |----------------|---------|----------------| | success | boolean | Always false | | errorMessage | string | Error details |

Run editor script

The run_method_in_unity tool invokes a static method on Unity Editor via reflection. Console logs during the method will be captured and returned in the logs field of the response.

[!TIP]
You can use this tool to edit scene and prefab files.

Parameters

| Name | Required | Description | |----------------|--------------|--------------------------------------------------------------------| | assemblyName | Required | Assembly name containing the type (e.g., Assembly-CSharp-Editor) | | typeName | Required | Fully qualified type name (e.g., MyNamespace.MyEditorTool) | | methodName | Required | Static method name to invoke (e.g., DoSomething) |

The method must be static and parameterless.

Response

| Field | Type | Description | |-----------|---------|---------------------------------------------------------------------------------------------------------------------------------------------------------| | success | boolean | Always true (indicates reflection succeeded; does not mean the method executed without errors — internal exceptions are captured in logs) | | logs | array | Console log entries captured during execution (may be empty). Each entry has type ("Message", "Warning", "Error"), message, and stackTrace. |

[!IMPORTANT]
The method's return value is NOT returned. success only indicates whether the method was found and invoked (reflection succeeded). Even if the method throws internally, success may be true — the exception is captured in the logs field.

[!IMPORTANT]
Async methods can be invoked, but the tool does not await their completion. Logs generated after return to the caller will not be included in the response.

Error Response

| Field | Type | Description | |----------------|---------|----------------| | success | boolean | Always false | | errorMessage | string | Error details |

Check compilation

The get_unity_compilation_result tool triggers Unity's AssetDatabase.Refresh() and checks if compilation succeeded. Console logs during compilation will be captured and returned in the logs field of the response.

Parameters: none

Response

| Field | Type | Description | |-----------|---------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| | success | boolean | Always true | | logs | array | Console log entries captured during compilation (may be empty). Each entry has type ("Message", "Warning", "Error"), message, and stackTrace. |

Error Response

| Field | Type | Description | |----------------|---------|---------------------------------------------------------------------------------------------------------------------------------------------------------| | success | boolean | Always false | | errorMessage | string | Error details | | logs | array | Console log entries captured before the error (may be empty). Each entry has type ("Message", "Warning", "Error"), message, and stackTrace. |

[!WARNING]
If the Unity Editor was compiled before this tool triggered a refresh, the response will not include a log. Compilation errors will remain in the console window, but will not be available with this tool. Instead, use the getDiagnostics or get_file_problems tools, or read editor.log.

[!TIP]
Recommended to run this tool to ensure compilation succeeds before run_unity_tests or run_method_in_unity tool if modified code.

Play mode control

The unity_play_control tool controls Unity Editor's play mode.

Parameters

| Name | Required | Description | |----------|--------------|----------------------------------------------------------------------------------------------| | action | Required | Action to perform: play, stop, pause, resume, step, or status (case insensitive) |

| Action | Operation | |----------|---------------------------------------------------| | play | Enter play mode | | stop | Exit play mode | | pause | Pause while in play mode | | resume | Resume from paused state | | step | Advance one frame (enters paused play mode) | | status | Read current play/pause state without any changes |

Response

| Field | Type | Description | |-------------|---------|------------------------------------------------| | success | boolean | Always true | | action | string | The action that was performed | | isPlaying | boolean | Whether Unity Editor is currently in play mode | | isPaused | boolean | Whether Unity Editor is currently paused |

Error Response

| Field | Type | Description | |----------------|---------|----------------| | success | boolean | Always false | | errorMessage | string | Error details |

Architecture

Coding Agent (e.g., Claude Code)
    ↓ MCP (HTTP/SSE)
JetBrains MCP Server (built into Rider 2025.2+)
    ↓ extension point (com.intellij.mcpServer)
[This Plugin — Kotlin Frontend]
    ├── UnityEditorToolset.kt (facade → CompilationResultTool / RunUnityTestsTool / RunMethodInUnityTool / PlayControlTool)
    │       ↓ (unity_play_control, get_unity_compilation_result, run_method_in_unity)
    │   FrontendBackendModel.playControls / FrontendBackendModel.runMethodInUnity / UnityTestMcpModel.getCompilationResult
    │       ↓ (run_unity_tests)
    │   UnityTestMcpModel (custom Rd: IRdCall<McpRunTest