IntelliJ IDEA MCP Skill

MCP is self-describing - this skill only documents known pitfalls and best practices not covered by MCP descriptions.

🚨 Critical Pitfalls (MCP Doesn't Warn You)

Connection Requirements

• •IDEA MUST be running with MCP server connected
• •Commands fail silently if IDEA is not running - no clear error message

Path Confusion (Most Common Error)

• •projectPath: ABSOLUTE PATH to project root (e.g., /Users/name/project)
  • •❌ project (wrong - relative)
  • •✅ /Users/name/project (correct - absolute)
• •filePath/pathInProject/directoryPath: RELATIVE to project root

Search Command Schema Bugs

MCP claims parameters are optional but they're REQUIRED:

• •

  search_in_files_by_text & search_in_files_by_regex: MUST include maxUsageCount

  • •Without this → schema error
  • •Start with maxUsageCount: 10
• •

  find_files_by_name_keyword & find_files_by_glob: MUST include fileCountLimit

  • •Without this → schema error "data must have required property 'probablyHasMoreMatchingFiles'"
  • •Known bug: Schema validation fails with certain patterns:
    • •find_files_by_name_keyword: Start with fileCountLimit: 1
    • •find_files_by_glob: Start with fileCountLimit: 5-7
    • •Broader patterns (e.g., **/*.java) may support higher limits
    • •If schema error, try smaller fileCountLimit or different patterns

Rename Refactoring Limitations

⚠️ MCP doesn't document what rename_refactoring CANNOT do:

• •✅ Renames: Field/variable declarations and their references
• •❌ May have limitations with: Method parameters in signatures, certain symbol types (test before relying)
• •Always use search_in_files_by_text first to understand scope
• •Always verify with get_file_problems after renaming

High-Risk Operations

MCP doesn't emphasize danger levels:

• •execute_terminal_command: HIGH RISK - Can run ANY shell command with full system permissions (no sandboxing). Use with extreme caution; verify commands before execution.
• •rename_refactoring & replace_text_in_file: Modifies code globally
• •create_new_file: Creates files on disk immediately
• •reformat_file: Modifies formatting without confirmation

✅ Essential Best Practices

1. •Path discipline: Absolute for projectPath, relative for everything else
2. •Count parameters: Always include maxUsageCount for search, fileCountLimit for file search
3. •File search: Start conservative - fileCountLimit: 1 for name keyword, 5-7 for glob
4. •Before refactoring: Search first to understand scope
5. •After changes: Use get_file_problems to verify no errors introduced
6. •Java accuracy: Prefer IDEA's get_file_problems over LSP (avoids false positives)
7. •Text replacement: Get exact text with get_file_text_by_path before replacing
8. •Test execution: Use execute_run_configuration for proper TeamCity-formatted output
9. •Timeouts: Build/test may need 120-300s, not default 30s

🔄 Common Workflows (Dongting Project)

Note: Examples use project path /Users/huangli/dt/dongting. Adjust projectPath for other projects.

1. Find a Java Class by Name

Use case: Locate KvImpl.java in the codebase.

Tool: IntelliJ-IDEA_find_files_by_name_keyword
Parameters:
  projectPath: "/Users/huangli/dt/dongting"  # Absolute path
  nameKeyword: "KvImpl"
  fileCountLimit: 1  # Start with 1 due to schema bug

If no results: Try find_files_by_glob with pattern:

Tool: IntelliJ-IDEA_find_files_by_glob
Parameters:
  projectPath: "/Users/huangli/dt/dongting"
  globPattern: "**/*KvImpl*.java"
  fileCountLimit: 5

2. Search for Text Across Codebase

Use case: Find all occurrences of "DtLog.getLogger".

Tool: IntelliJ-IDEA_search_in_files_by_text
Parameters:
  projectPath: "/Users/huangli/dt/dongting"
  searchText: "DtLog.getLogger"
  maxUsageCount: 20  # REQUIRED parameter
  caseSensitive: true

For regex patterns (e.g., find all log declarations):

Tool: IntelliJ-IDEA_search_in_files_by_regex
Parameters:
  projectPath: "/Users/huangli/dt/dongting"
  regexPattern: "private static final DtLog log = DtLogs\\.getLogger\\(.*\\)"
  maxUsageCount: 10

3. Run a Test via IDEA Run Configuration

Use case: Execute the "client:test" run configuration.

Tool: IntelliJ-IDEA_execute_run_configuration
Parameters:
  projectPath: "/Users/huangli/dt/dongting"
  configurationName: "client:test"
  timeout: 120000  # 2 minutes for tests

First, list available run configurations:

Tool: IntelliJ-IDEA_get_run_configurations
Parameters:
  projectPath: "/Users/huangli/dt/dongting"

4. Check Compilation Errors in a File

Use case: Verify server/src/main/java/com/github/dtprj/dongting/raft/server/RaftNode.java has no errors.

Tool: IntelliJ-IDEA_get_file_problems
Parameters:
  projectPath: "/Users/huangli/dt/dongting"
  filePath: "server/src/main/java/com/github/dtprj/dongting/raft/server/RaftNode.java"
  errorsOnly: true

Note: More accurate than LSP for this multi-module Maven project.

5. Safe Refactoring: Rename a Field

Pre-verification: Search for current usage:

Tool: IntelliJ-IDEA_search_in_files_by_text
Parameters:
  projectPath: "/Users/huangli/dt/dongting"
  searchText: "currentTerm"
  maxUsageCount: 50

Execute rename:

Tool: IntelliJ-IDEA_rename_refactoring
Parameters:
  projectPath: "/Users/huangli/dt/dongting"
  pathInProject: "server/src/main/java/com/github/dtprj/dongting/raft/server/RaftNode.java"
  symbolName: "currentTerm"
  newName: "currentElectionTerm"

Post-verification: Check for errors:

Tool: IntelliJ-IDEA_get_file_problems
Parameters:
  projectPath: "/Users/huangli/dt/dongting"
  filePath: "server/src/main/java/com/github/dtprj/dongting/raft/server/RaftNode.java"

6. Explore Project Structure

Use case: View module layout.

Tool: IntelliJ-IDEA_list_directory_tree
Parameters:
  projectPath: "/Users/huangli/dt/dongting"
  directoryPath: "."  # Project root
  maxDepth: 3

To see all open files (helpful for context):

Tool: IntelliJ-IDEA_get_all_open_file_paths
Parameters:
  projectPath: "/Users/huangli/dt/dongting"

🤔 When to Use: IDEA MCP vs LSP vs Bash Tools

Decision Matrix

Key Principles

1. •IDEA MCP when: Need IDE intelligence (refactoring, accurate errors, test execution)
2. •LSP when: Quick file reads, symbol navigation (if IDEA not available)
3. •Bash when: Builds, Git, system operations, or when IDEA MCP has schema bugs

Remember: IDEA must be running for MCP tools to work. If IDEA is unavailable, fall back to LSP/Bash.

⏱️ Performance Considerations & Timeouts

Recommended Timeouts by Operation

Performance Tips

1. •Limit search results: Use maxUsageCount and fileCountLimit to avoid excessive data transfer
2. •Cache project state: IDEA MCP maintains project index; repeated searches are faster
3. •Avoid redundant calls: Use get_all_open_file_paths to see what's already loaded
4. •Batch operations: Combine searches with careful planning (but MCP is stateless)
5. •Fallback for large operations: For full project builds, use Bash mvn commands instead

Memory & Resource Considerations

• •IDEA MCP runs within IDEA's JVM; large operations may affect IDE performance
• •Searching huge files (>10MB) may cause timeouts; use LSP read with offset/limit instead
• •Concurrent MCP requests may queue; avoid parallel operations on same project

🔧 Quick Troubleshooting

Common Error Messages and Solutions

"Structured content does not match" (schema error)

• •Add missing maxUsageCount or fileCountLimit parameter
• •For file search errors: Try smaller fileCountLimit values

Commands fail/timeout

1. •Verify IDEA is running with MCP server connected
2. •Check MCP plugin is active in IDEA settings
3. •Wait for connection (may take seconds)
4. •Verify project is fully loaded in IDEA

Search returns no results

1. •Verify projectPath is absolute and correct
2. •Verify file paths are relative to project root
3. •Use list_directory_tree to verify structure exists

File operation fails

• •For create_new_file: Use overwrite: true if file exists
• •For replace_text_in_file: Get exact text with get_file_text_by_path first
• •Check file is not locked by another process