using-lsp-tools

Auto-invocation: Your coding assistant will automatically invoke this skill when it detects a matching trigger.

Use when mcp-language-server tools are available and you need semantic code intelligence. Triggers: 'find definition', 'find references', 'who calls this', 'rename symbol', 'type hierarchy', 'go to definition', 'where is this used', 'where is this defined', 'what type is this'. Provides navigation, refactoring, and type analysis via LSP.

Skill Content

# Using LSP Tools

<ROLE>
Language Tooling Expert. Reputation depends on leveraging semantic analysis over text matching for accurate, complete code navigation and refactoring.
</ROLE>

## Invariant Principles

1. **Semantic > Lexical**: LSP understands scope, types, inheritance. Grep sees text.
2. **LSP for Symbols, Grep for Strings**: Symbols = definitions, references, types. Strings = TODOs, comments, literals.
3. **Verify Before Fallback**: Empty LSP result? Check file saved. Then try text-based.
4. **Atomic Operations Preferred**: `rename_symbol` handles all files. Manual Edit misses references.

## Reasoning Schema

<analysis>
- Is target a symbol (function, class, variable) or literal text?
- Is LSP server active for this language?
- Does task need semantic understanding (types, scope, inheritance)?
</analysis>

<reflection>
- Did LSP return expected results? If empty: file saved? Feature supported?
- Did fallback find matches LSP missed? Indicates LSP limitation vs. saved state.
</reflection>

## Inputs

| Input | Required | Description |
|-------|----------|-------------|
| `filePath` | Yes | Absolute path to file being analyzed |
| `line` | Context | 1-indexed line number for position-based queries |
| `column` | Context | 1-indexed column for position-based queries |
| `symbolName` | Context | Fully-qualified name for definition/references |
| `language` | No | Language identifier if ambiguous |

## Outputs

| Output | Type | Description |
|--------|------|-------------|
| Symbol locations | Inline | File paths and positions from navigation queries |
| Type information | Inline | Hover/signature data for understanding |
| Refactoring edits | Applied | Direct code modifications from rename/actions |
| Diagnostics | Inline | Errors and warnings for debugging |

## Tool Priority Matrix

| Task | LSP Tool | Fallback |
|------|----------|----------|
| Find definition | `definition` | Grep `func X\|class X\|def X` |
| Find usages | `references` | Grep symbol name |
| Understand symbol | `hover` | Read + infer |
| Rename | `rename_symbol` | Multi-file Edit (risky) |
| File outline | `document_symbols` | Grep definitions |
| Callers | `call_hierarchy` incoming | Grep + analyze |
| Callees | `call_hierarchy` outgoing | Read function |
| Type hierarchy | `type_hierarchy` | Grep extends/implements |
| Workspace search | `workspace_symbol_resolve` | Glob + Grep |
| Refactorings | `code_actions` | Manual |
| Signature | `signature_help` | Hover or read |
| Diagnostics | `diagnostics` | Build command |
| Format | `format_document` | Formatter CLI |
| Edit by line | `edit_file` | Built-in Edit |

## Parameters

Required: `filePath` (absolute), `line`/`column` (1-indexed), `symbolName` (fully-qualified for definition/references).

## Decision Rules

**Use LSP when:**
- Finding true definition (not text match)
- Refactoring (rename, extract, inline)
- Understanding type relationships
- Finding semantic usages
- Cross-file navigation via imports

**Use Grep/Glob when:**
- Literal strings, comments, non-code text
- Regex patterns
- LSP returns empty but code exists
- Unsupported languages
- Non-symbols (TODOs, URLs, magic strings)

## Workflows

**Exploration:** `document_symbols` (structure) -> `hover` (types) -> `definition` (jump) -> `references` (usage)

**Refactoring:** `code_actions` (discover) -> `rename_symbol` (execute) OR `references` (assess impact) -> manual

**Type debugging:** `hover` (inferred) -> `type_hierarchy` (inheritance) -> `diagnostics` (errors)

**Call analysis:** `call_hierarchy` incoming = "who calls?" | outgoing = "what calls?"

## Anti-Patterns

<FORBIDDEN>
- Using Grep for symbol rename (misses scoped references, hits false positives)
- Skipping LSP for "simple" refactors (simple becomes complex with inheritance)
- Trusting empty LSP results without checking file saved state
- Manual multi-file edits when `rename_symbol` available
- Ignoring `diagnostics` output when debugging type errors
</FORBIDDEN>

## Fallback Protocol

1. LSP error/empty -> Check file saved (LSP reads disk)
2. Try table fallback
3. Persistent failure -> Feature unsupported by server

## Self-Check

Before completing:
- [ ] Used semantic LSP tool for symbol-based queries (not text search)
- [ ] Verified file saved if LSP returned empty/unexpected results
- [ ] Applied atomic refactoring operations where available
- [ ] Documented fallback rationale if LSP bypassed

If ANY unchecked: STOP and reconsider approach.