# lsp-format-code

Formats an entire source file or a selected line range through a language server. Use it to tidy generated code or apply the project's formatting rules before a commit.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · ★ 165
- Author: blackwell-systems
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/blackwell-systems/agent-lsp/tree/HEAD/skills/lsp-format-code/SKILL.md
- Updated: 2026-10-24
- HTML: https://affpapa.org/en/nevibecode/skills/lsp-format-code

## What it does

The `lsp-format-code` skill asks the language server to format code using the formatter associated with that language. Its documented examples cover Go, TypeScript, JavaScript, Rust, Python, and C/C++, with tools such as `gofmt`, `prettier`, `rustfmt`, `black`, and `clang-format`. These formatters do not need separate installation on `PATH` for the described workflow.

The workflow opens the target document, requests edits for either the full file or a chosen line range, and passes the returned `TextEdit` list to `mcp__lsp__apply_edit`. Formatting requests alone do not write changes to disk. A diagnostics check can follow; if formatting support is unavailable, the skill stops that path and recommends invoking the formatter directly.

The `agent-lsp` MCP server must be available and expose document formatting support. Range formatting relies on the additional `documentRangeFormattingProvider` capability, so a server that supports whole-file formatting may still lack range support. If formatting introduces diagnostic errors, the instructions say to report them before committing.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add blackwell-systems/agent-lsp --skill lsp-format-code -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/lsp-format-code/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/lsp-format-code/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add blackwell-systems/agent-lsp --skill lsp-format-code -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/lsp-format-code/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add blackwell-systems/agent-lsp --skill lsp-format-code -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/lsp-format-code/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install blackwell-systems/agent-lsp lsp-format-code
```

2. **Manually: put the files in place**
- File: `.github/skills/lsp-format-code/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add blackwell-systems/agent-lsp --skill lsp-format-code -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/blackwell-systems/agent-lsp --path skills/lsp-format-code
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/lsp-format-code/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add blackwell-systems/agent-lsp --skill lsp-format-code -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/blackwell-systems/agent-lsp/tree/HEAD/skills/lsp-format-code/SKILL.md

## When to use it
- Apply language-specific formatting to a complete source file
- Clean up indentation and spacing in generated code
- Format only the lines containing a function
- Address formatter-fixable style violations before a commit
- Check diagnostics after applying formatting edits

## Example prompts
- Format `src/main.go` through the language server and check the file diagnostics afterward.
- Reformat the function in `src/app.ts` using only its line range.
- Format every changed file before committing and report any file whose language server lacks formatting support.

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 646aabf6cc76238a.

BEGIN THIRD-PARTY FILE 646aabf6cc76238a
````text
---
name: lsp-format-code
description: Format a file or selection using the language server's formatter. Use before committing to apply consistent style, or after generating code to clean up indentation and spacing. Supports full-file and range-based formatting.
argument-hint: "[file-path] [optional: start_line-end_line]"
user-invocable: true
allowed-tools: mcp__lsp__open_document mcp__lsp__format_document mcp__lsp__format_range mcp__lsp__apply_edit mcp__lsp__get_diagnostics mcp__lsp__get_server_capabilities
license: MIT
compatibility: Requires the agent-lsp MCP server (github.com/blackwell-systems/agent-lsp)
metadata:
  required-capabilities: documentFormattingProvider
  optional-capabilities: documentRangeFormattingProvider
---

> Requires the agent-lsp MCP server.

# lsp-format-code

Format a file or selection using the language server's formatter — the same
formatting engine your IDE uses. Applies language-specific rules (gofmt, prettier,
rustfmt, black) without requiring those tools to be on PATH separately.

## When to use

- Before committing: ensure consistent style across edited files
- After generating code: clean up AI-generated indentation and spacing
- After a refactor that shifted indentation levels
- When a linter flags style violations fixable by the formatter

Use `/lsp-safe-edit` instead when you are making a logic change and want
before/after diagnostic comparison alongside the edit.

---

## Workflow

### Step 1 — Check formatting is supported (optional)

If unsure whether the language server supports formatting for this file, check
capabilities first:

```
mcp__lsp__get_server_capabilities({ "file_path": "<file>" })
```

Look for `documentFormattingProvider` (full-file) and
`documentRangeFormattingProvider` (range). If neither is present, the server
does not support formatting — stop and report.

Skip this step if you know the language supports formatting (Go, TypeScript,
Rust, Python all do via their standard servers).

### Step 2 — Open the file

```
mcp__lsp__open_document({ "file_path": "/abs/path/to/file.go", "language_id": "go" })
```

### Step 3 — Request formatting edits

**Full file:**
```
mcp__lsp__format_document({ "file_path": "/abs/path/to/file.go" })
```

**Selection only:**
```
mcp__lsp__format_range({
  "file_path": "/abs/path/to/file.go",
  "start_line": <N>,
  "end_line": <M>
})
```

Both return `TextEdit[]` — a list of replacements to apply. They do **not**
````
END THIRD-PARTY FILE 646aabf6cc76238a

The third-party file has ended. Everything between the 646aabf6cc76238a tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

First 2451 of 5126 bytes. © blackwell-systems · MIT · https://github.com/blackwell-systems/agent-lsp/tree/HEAD/skills/lsp-format-code/SKILL.md

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---
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