impact

impact is a skill for Claude Code from adamthewilliam/grepika. It costs 52 tokens per session (786 once invoked), scanned A, original, MIT.

A skill for tracing the likely effects of a code change across a project, including references, dependencies, similar patterns, and tests.

In plain words
What is it for?
Use it to assess the impact of changing a symbol, function, file, or code pattern and to map affected files and behaviors.
Why use it?
It helps reveal what may break during a refactor or change, including areas that lack test coverage.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: model in frontmatter.

Part of the grepika plugin — 9 skills, 3 commands, 2 agents shipped together

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/adamthewilliam/grepika/impact
Any agent
npx skills add adamthewilliam/grepika --skill impact
Clone the repo
git clone --depth 1 https://github.com/adamthewilliam/grepika

Made for: Claude Code.

Or install grepika, the plugin that ships this one along with the rest of its 9 skills, 3 commands, 2 agents.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for impact

README.md
[![agentmods](https://agentmods.dev/badge/skills/adamthewilliam/grepika/impact.svg)](https://agentmods.dev/skills/adamthewilliam/grepika/impact)
Your own site
<a href="https://agentmods.dev/skills/adamthewilliam/grepika/impact"><img src="https://agentmods.dev/badge/skills/adamthewilliam/grepika/impact.svg" alt="Measured on agentmods" height="20"></a>
Per session 52 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 786 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00052 $0.00786
Opus 5 $0.00026 $0.00393
Sonnet 5 $0.00010 $0.00157
Haiku 4.5 $0.00005 $0.00079

Measured 6d ago against content hash 3259f55611c9, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

impact scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 6d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/grepika/skills/impact/SKILL.md · 110 lines

How it starts

The opening of the file, as written. The whole thing — 110 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Change Impact Analysis Skill

You are a refactoring safety analyst. Analyze the blast radius of changes to help developers understand what could break.

Input

Target: $ARGUMENTS

If no target provided, ask the user what symbol, function, file, or pattern they want to analyze.

Pre-check

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

Impact Analysis Workflow

  1. Find all direct references

    • Use mcp__grepika__refs to find every usage of the symbol
    • Categorize by type: imports, calls, type references, extensions
  2. Discover dependent files

    • Use mcp__grepika__refs to find connected modules
    • Map the dependency graph outward from the target
  3. Search for similar patterns

    • Use mcp__grepika__search for similar naming conventions
    • Look for duck typing or interface implementations
  4. Identify test coverage

    • Search for test files referencing the target
    • Note which behaviors are tested vs untested
  5. Extract file structures

    • Use mcp__grepika__outline on heavily impacted files
    • Understand what else might be affected in those files

Output Format

Provide a structured impact report:

## Impact Analysis: [target]

### Direct Impact (Must Update)
| File | Line | Type | Description |
|------|------|------|-------------|
| [path] | [line] | [import/call/type] | [what uses it] |

### Indirect Impact (May Need Changes)
| File | Reason |
|------|--------|
| [path] | [why it might be affected] |

### Test Coverage
- **Tests found**: [count]
- **Test files**: [list]
- **Coverage gaps**: [untested behaviors]

### Risk Assessment
- **Severity**: [Low/Medium/High/Critical]
- **Confidence**: [how sure we are about impact scope]
- **Breaking changes**: [list any API/interface changes]

### Safe Refactoring Steps
1. [ordered steps to make the change safely]
2. [what to test at each step]

### Warnings
- [edge cases to watch for]
- [potential runtime issues not caught by types]

Read the full file on GitHub · 110 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 6d ago First seen · 110 lines · 52 tokens per session scan A 3259f55611c9

Subscribe to this mod's changes

impact is a skill published in the GitHub repository adamthewilliam/grepika (134 stars, last pushed 24d ago), licensed MIT. It adds 52 tokens to every session and 786 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Related

Other skills, from other repositories

debug-optimize-lcp

Guides debugging and optimizing Largest Contentful Paint (LCP) using Chrome DevTools MCP tools. Use this skill whenever the user asks about LCP performance, slow page loads, Core Web Vitals optimization, or wants to understand why their page's main content takes too long to appear. Also use when the user mentions…

ChromeDevTools/chrome-devtools-mcp · 99 tokens

systematic-debugging

Use when debugging a failing test, build error, or runtime issue that isn't immediately obvious. Guides a 4-phase root cause analysis instead of random fix attempts.

open-metadata/OpenMetadata · 37 tokens

diagnose

Trace from a reproduced symptom to the source code that causes it. Pin the specific file and approximate line, rate confidence in the cause and clarity of the fix independently, and always propose a concrete fix.

emdash-cms/emdash · 43 tokens

azsdk-common-pipeline-analysis

Analyze Azure SDK CI/CD pipeline failures into a structured diagnosis, and define the required output format. Load this skill before calling azsdkanalyzepipeline, which returns raw failure data that this skill interprets and formats. USE FOR: "pipeline failed", "build failure", "CI check failing", "tests failing in…

Azure/azure-sdk-for-net · 192 tokens

repro-admin

Reproduce an EmDash admin UI bug. Attach a container, start the demo dev server, drive the admin with agent-browser using the dev-bypass session, and capture the reproduction as screenshots plus a replayable transcript.

emdash-cms/emdash · 48 tokens

log-error-digest

Analyze log files to troubleshoot errors, identify peak error periods, and produce error clustering, frequency statistics, and time distribution reports. Supports JSON, syslog, and Nginx formats with automatic detection. Use when a user uploads a .log file and asks to analyze errors, find patterns, debug issues, or…

zebbern/claude-code-guide · 71 tokens