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.
npx skills add sigistry/marketplace --skill breaking-change-detectiongit clone --depth 1 https://github.com/sigistry/marketplaceWrote 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.
[](https://agentmods.dev/skills/sigistry/marketplace/breaking-change-detection)<a href="https://agentmods.dev/skills/sigistry/marketplace/breaking-change-detection"><img src="https://agentmods.dev/badge/skills/sigistry/marketplace/breaking-change-detection/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/sigistry/marketplace/breaking-change-detection"><img src="https://agentmods.dev/badge/skills/sigistry/marketplace/breaking-change-detection.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00073 | $0.00874 |
| Opus 5 | $0.00036 | $0.00437 |
| Sonnet 5 | $0.00015 | $0.00175 |
| Haiku 4.5 | $0.00007 | $0.00087 |
Grade A, and why
breaking-change-detection 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 7d 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.
How it starts
The opening of the file, as written. The whole thing — 68 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Breaking Change Detection
Purpose
Standardize how a change is classified against Semantic Versioning by reasoning about its effect on consumers, including behavioral breaks that leave the syntax intact. Humans get binary compatibility right only about 60% of the time; this methodology closes the gap with an explicit decision matrix and per-ecosystem catalogs. Tech-agnostic.
First: is the change on the public surface?
Only changes to the public API surface can be breaking or minor. Establish the surface before classifying (detailed per ecosystem in references/breaking-change-catalog.md):
| Ecosystem | Public surface |
|---|---|
| JS/TS | package.json exports/main, named/default exports, .d.ts |
| Python | __all__, non-_ names, entry points |
| Go | Capitalized identifiers outside internal/ |
| Java/C# | public/protected members of exported packages |
| Rust | pub items reachable from the crate root |
| CLI | flags, subcommands, arg order, exit codes, stdout format |
| HTTP | routes, methods, request/response schema, status codes |
| GraphQL | types, fields, args, nullability, enum values |
| Config | recognized keys, env vars, defaults |
A change entirely within private/internal code is at most a PATCH.
The decision matrix
| Change | Classification |
|---|---|
| Remove/rename a public export, field, route, flag, env var | MAJOR |
| Change a signature (add required param, reorder, retype, change return type) | MAJOR |
| Change a default value that alters observable behavior | MAJOR |
| Make validation stricter (reject formerly-valid input) | MAJOR |
| Change output shape, field names, units, or serialization | MAJOR |
| Change/narrow error or exception types, or HTTP status codes | MAJOR |
| Remove an enum value or change its meaning | MAJOR |
| Add a new public export/endpoint/optional param/flag | MINOR |
| Add an optional field to output (additive) | MINOR |
| Loosen validation (accept more input) | MINOR (usually) |
| Deprecate without removing | MINOR |
| Bug fix restoring documented behavior | PATCH |
| Performance improvement, no behavior change | PATCH |
| Internal refactor, docs, tests, CI | PATCH / no release |
What ships with it
2 files 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.
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.
- 7d ago First seen · 68 lines · 73 tokens per session scan A 94b4f13ccd83
breaking-change-detection is a skill published in the GitHub repository sigistry/marketplace (3 stars, last pushed today), licensed MIT. It adds 73 tokens to every session and 874 once invoked, about $0.0004 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 2026-09-03.
Other skills, from other repositories
pr
Comprehensive PR/issue review - analyzes architecture, tests, identifies unrelated changes mixed in, drafts review comment or issue comment. Use when user asks to review a PR, check a PR, look at PR changes, or comment on an issue.
backlog
Read, work, and maintain a Git repo's deferred-work items in docs/backlog/, one file per item. Use when the user says "backlog", "check backlog", "what's on my backlog", "work the backlog", "address the backlog", "add to backlog", "clean up backlog", or when a review or task produced items that are real but not being…
last-tag
Show commits since the last tag in a formatted table. Use when user asks "what changed since last release", "commits since last tag", "last-tag", "what's new", or wants to see recent unreleased changes.
glab
Expert guidance for using the GitLab CLI (glab) to manage GitLab issues, merge requests, CI/CD pipelines, repositories, and other GitLab operations from the command line. Use this skill when the user needs to interact with GitLab resources or perform GitLab workflows.
version-bump
This skill automates version bumping during the release process for the Claude Code Handbook monorepo. It should be used when the user requests to bump versions, prepare a release, or increment version numbers across the repository.
commit-push-pr
Full git workflow - creates branch, commits, pushes, and creates or updates a PR with summary and test plan.