IDE Diagnostics MCP

Use the getidediagnostics MCP tool to answer "what is this IDE doing right now?" from inside a running IntelliJ process.

This skill is for live IDE process evidence only. If the request is to diagnose an arbitrary issue, inspect repository code, analyze build/test output, or debug the MCP server itself, use the relevant debugging, testing, or code-investigation workflow instead.

Availability

The diagnostics toolset is hidden unless the IDE was started with:

-Didea.diagnostics.mcp.enabled=true

If getidediagnostics is not available, tell the user the IDE must be restarted with that property. Do not confuse it with MCP server self-diagnostics; the property enables IDE process diagnostics exposed through MCP.

Capture Workflow

Start with a lightweight CPU sample without the raw dump:

{
  "sampleMillis": 1000,
  "topThreadCount": 25,
  "includeRawDump": false
}

For freezes, blocked threads, or coroutine investigation, request a bounded raw dump:

{
  "sampleMillis": 1000,
  "topThreadCount": 50,
  "includeRawDump": true,
  "maxDumpChars": 200000,
  "stripCoroutineDump": true
}

For action-specific performance questions, take one sample before or during the action and another while the symptom is visible. Compare topCpuThreads, blockedCountDelta, waitedCountDelta, and threads.stateCounts between samples.

Interpretation

• process.processCpuLoad and process.systemCpuLoad are point-in-time process/system CPU load values; -1 means the JVM cannot provide the metric.
• topCpuThreads[].cpuDeltaNanos ranks threads by CPU consumed during sampleMillis; -1 means thread CPU time is unavailable.
• topCpuThreads[].state is the JVM Thread.State; RUNNABLE includes Java execution and native calls, including native I/O.
• topCpuThreads[].isInNative, nativeFrame, and nativeOperationHint help identify native calls, but they are not OS wait-channel data.
• topCpuThreads[].stackTrace is a short stack snapshot for attribution, not a full profiler call tree.
• threads.stateCounts is useful for spotting many BLOCKED, WAITING, or TIMED_WAITING threads.
• rawDump is the IntelliJ thread dump text and may include coroutine dump content when coroutine dumping is enabled in the running IDE.
• rawDumpTruncated=true means repeat with a larger maxDumpChars or ask for a narrower next step before drawing conclusions from missing tail content.
• coroutineDumpEnabled=false means the tool cannot provide coroutine dump details beyond ordinary thread stacks.

Escalation

Use this MCP tool for low-overhead triage and evidence gathering. For root-cause CPU attribution, allocation pressure, lock profiling, native wait-state attribution, or long recordings, ask for JFR, async-profiler, or the IDE's standard performance capture workflow.