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Agent skill

Diff Files

by adamthewilliam in adamthewilliam/grepika

This skill should be used when the user asks to "compare files", "diff these files", "what changed between", "show differences between", "compare versions", or mentions keywords related to file…

MITAuto-check passedDevelopment

Install Diff Files

skills CLI
$ npx skills add adamthewilliam/grepika --skill diff-files -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install adamthewilliam/grepika diff-files --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/adamthewilliam/grepika.git skills-src && mkdir -p .claude/skills && cp -r skills-src/plugins/grepika/skills/diff-files .claude/skills/diff-files && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
diff-files
GitHub stars
138
Token cost
~819 tokens
SKILL.md length
242 words
Files
1
Skills in repo
9
Repo updated
First seen
Licence
MIT

At a glance

This skill should be used when the user asks to "compare files", "diff these files", "what changed between", "show differences between", "compare versions", or mentions keywords related to file…

  • Works in 5 steps: Parse the input → Get file outlines first (optional, for… → Run the diff → …
  • Asks to compare files
  • SKILL.md covers Input, Pre-check, Comparison Workflow and Output Format, plus 2 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Diff Files is an agent skill from adamthewilliam/grepika. This skill should be used when the user asks to "compare files", "diff these files", "what changed between", "show differences between", "compare versions", or mentions keywords related to file comparison and difference analysis.

Its SKILL.md is about 820 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts. Compatibility notes: Requires grepika MCP server.

It sits in Development. It works with Model Context Protocol. The licence is MIT.

When your agent uses it

  • Asks to compare files
  • Diff these files
  • What changed between
  • Show differences between

Example prompts

  • “compare files”
  • “diff these files”
  • “what changed between”
  • “/diff-files”

Requirements

  • Compatibility (from SKILL.md): Requires grepika MCP server.
  • Pre-approved tools (allowed-tools): mcp__grepika__diff, mcp__grepika__get, mcp__grepika__outline, mcp__grepika__add_workspace

Workflow steps

5 steps, taken from the first numbered list in SKILL.md.

  1. Parse the input
  2. Get file outlines first (optional, for large files)
  3. Run the diff
  4. Analyze the differences
  5. Get context if needed

What it can do on your machine

Read from SKILL.md and the folder at commit f035a18. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves these tools, so the agent can use them without asking each time:

    • mcp__grepika__diff
    • mcp__grepika__get
    • mcp__grepika__outline
    • mcp__grepika__add_workspace

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

  • Compatibility

    Requires grepika MCP server.

    From compatibility in the SKILL.md frontmatter.

Context cost

Diff Files loads about 819 tokens when it runs. Until then it costs about 60 tokens; SKILL.md has 242 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~60
When it runs · the whole SKILL.md, loaded when a task matches
~819

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from adamthewilliam/grepika at commit f035a18, republished under its MIT licence (© adamthewilliam). 242 words, ~819 tokens.

Download SKILL.mdSave it as .claude/skills/diff-files/SKILL.md (or your agent's skills folder).
name
diff-files
description
This skill should be used when the user asks to "compare files", "diff these files", "what changed between", "show differences between", "compare versions", or mentions keywords related to file comparison and difference analysis.
allowed-tools
mcp__grepika__diff, mcp__grepika__get, mcp__grepika__outline, mcp__grepika__add_workspace
compatibility
Requires grepika MCP server.
version
1.0.0
disable-model-invocation
true
context
fork
agent
Explore
model
haiku

File Comparison Skill

You are a file comparison specialist. Compare two files and explain the differences clearly.

Input

Files to compare: $ARGUMENTS

Expected formats:

  • file1.ts file2.ts - Compare two different files
  • file1.ts:10-50 file2.ts:10-50 - Compare specific line ranges
  • src/old.ts src/new.ts - Full paths work too

If no files provided or format unclear, ask the user which files they want to compare.

Pre-check

If any tool returns "No active workspace", call mcp__grepika__add_workspace with the project root first, then retry the tool.

Comparison Workflow

  1. Parse the input

    • Extract file paths from arguments
    • Identify any line range specifications
    • Handle both relative and absolute paths

  2. Get file outlines first (optional, for large files)

    • Use mcp__grepika__outline to understand each file's structure
    • Identify key sections to focus the comparison

  3. Run the diff

    • Use mcp__grepika__diff with the two file paths
    • The tool returns a unified diff format

  4. Analyze the differences

    • Categorize changes: additions, deletions, modifications
    • Identify the nature of changes: refactoring, bug fixes, feature additions
    • Note any structural changes (renamed functions, moved code)

  5. Get context if needed

    • Use mcp__grepika__get to read surrounding code for complex changes
    • Understand the purpose of each change

Output Format

## File Comparison

### Files Compared
- **File A**: [path] ([line count] lines)
- **File B**: [path] ([line count] lines)

### Summary
[1-2 sentence overview of what changed and why]

### Change Statistics
| Type | Count |
|------|-------|
| Lines added | [count] |
| Lines removed | [count] |
| Lines modified | [count] |

### Detailed Changes

#### [Change Category 1] (e.g., "Function Signature Changes")
| Location | Change | Impact |
|----------|--------|--------|
| [line] | [what changed] | [what this affects] |

#### [Change Category 2] (e.g., "New Logic Added")
[description of changes]

### Semantic Analysis
- **Type of change**: [refactor / bugfix / feature / breaking change]
- **Risk level**: [low / medium / high]
- **Backward compatible**: [yes / no / partial]

### Notable Observations
- [anything unusual or worth highlighting]
- [patterns in the changes]

Tips

  • Focus on the "why" behind changes, not just the "what"
  • Group related changes together for clarity
  • Highlight breaking changes prominently
  • For large diffs, summarize by section rather than line-by-line
  • Note if the diff suggests incomplete refactoring

Additional Resources

See references/ folder for:

  • Common diff patterns and their meanings
  • Code migration analysis techniques

© adamthewilliam, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in plugins/grepika/skills/diff-files of adamthewilliam/grepika.

Open the folder on GitHubat commit f035a18

Compare with similar skills

Diff Files next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Diff Files compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Diff Files this skilladamthewilliam/grepika138—~819Automated safety check: PassMIT
ast-grep Structural Searchcode-yeongyu/oh-my-openagent70k—~3.3kAutomated safety check: PassMIT
ReleasePrefectHQ/fastmcp28k—~2.9kAutomated safety check: PassApache-2.0
Claude Code Skillcodeaashu/claude-code3.4k1 repos~2.7kAutomated safety check: PassProprietary
Run Nx Generatornrwl/nx29k2 repos~592Automated safety check: NotesMIT
LangBot Plugin Developmentlangbot-app/LangBot18k—~3.9kAutomated safety check: PassApache-2.0

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  • Learn Codebase

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  • Apply Pattern

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  • Architecture

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Works with

Categories

Questions about Diff Files

What does Diff Files do?

This skill should be used when the user asks to "compare files", "diff these files", "what changed between", "show differences between", "compare versions", or mentions keywords related to file…. Diff Files is an agent skill from adamthewilliam/grepika. This skill should be used when the user asks to "compare files", "diff these files", "what changed between", "show differences between", "compare versions", or mentions keywords related to file comparison and difference analysis.

When should I use Diff Files?

Diff Files fits situations like: asks to compare files; diff these files; what changed between; show differences between.

How do I install Diff Files in Claude Code?

Run `npx skills add adamthewilliam/grepika --skill diff-files -a claude-code`. Or copy the skill folder (plugins/grepika/skills/diff-files in adamthewilliam/grepika) into .claude/skills/diff-files in your project. Claude Code loads it when a task matches its description.

How do I install Diff Files in Codex?

Run `npx skills add adamthewilliam/grepika --skill diff-files -a codex`. Or copy the skill folder (plugins/grepika/skills/diff-files in adamthewilliam/grepika) into .agents/skills/diff-files in your project. Codex loads it when a task matches its description.

Can I use Diff Files in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add adamthewilliam/grepika --skill diff-files -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/diff-files, .gemini/skills/diff-files, .github/skills/diff-files and .opencode/skills/diff-files in your project.

What does Diff Files need to run?

SKILL.md names no scripts, command-line tools or credentials: Diff Files is instructions for the agent only. Its frontmatter pre-approves these tools: mcp__grepika__diff, mcp__grepika__get, mcp__grepika__outline, mcp__grepika__add_workspace. Compatibility (from SKILL.md): Requires grepika MCP server..

Does Diff Files access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Diff Files safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Diff Files use?

Diff Files is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Diff Files use?

About 819 tokens (SKILL.md is roughly 3.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Diff Files?

Skills that share tags, products or a category with Diff Files: ast-grep Structural Search (code-yeongyu/oh-my-openagent, 70k stars), Release (PrefectHQ/fastmcp, 28k stars), Claude Code Skill (codeaashu/claude-code, 3.4k stars) and Run Nx Generator (nrwl/nx, 29k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Diff Files?

adamthewilliam (a GitHub user) maintains it in adamthewilliam/grepika, which has 138 GitHub stars. The repository holds 9 skills in this directory. The repository was last updated on August 12, 2026.

Source: adamthewilliam/grepika on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.