Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/stdin/buy-vs-buildnpx agentmods add skills/stdin/buy-vs-build/buy-vs-build-dependencyWrote 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/stdin/buy-vs-build/buy-vs-build-dependency)<a href="https://agentmods.dev/skills/stdin/buy-vs-build/buy-vs-build-dependency"><img src="https://agentmods.dev/badge/skills/stdin/buy-vs-build/buy-vs-build-dependency/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/stdin/buy-vs-build/buy-vs-build-dependency"><img src="https://agentmods.dev/badge/skills/stdin/buy-vs-build/buy-vs-build-dependency.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 | $0.00056 | $0.01040 |
| Opus 5 | $0.00028 | $0.00520 |
| Sonnet 5 | $0.00011 | $0.00208 |
| Haiku 4.5 | $0.00006 | $0.00104 |
Grade A, and why
buy-vs-build-dependency 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 10d 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 — 89 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Buy vs Build — Dependency Research
Adding a dependency means adopting its bugs, its maintainers' availability, its security posture, and its whole transitive tree. Research it before you own it. This checklist is the union of two best-in-class frameworks — Russ Cox, "Our Software Dependency Problem" (research.swtch.com/deps), and the OpenSSF "Concise Guide for Evaluating Open Source Software" (best.openssf.org) — plus bus-factor/sustainability research.
This applies to any ecosystem — npm, PyPI, Go modules, Maven, Cargo, NuGet, RubyGems, or anything else. You do the research: gather the signals below from the package's registry, its source repository, deps.dev, and OSV, then judge. The helper automates supported registries, but the checklist — and the judgment — is yours regardless of language.
Start by trying to avoid it
The cheapest dependency is the one you don't add. Before researching a package, confirm a lower rung does not already cover the need: a built-in, a native platform feature, or an already-installed dependency. Reach for a new dependency only when it clearly lowers total cost of ownership, and never for a few clear lines you could own outright (remember left-pad).
The checklist
Fit & necessity
- Does it solve the actual requirement without large unused surface area?
- Is the API well-designed, documented, and stable (stable APIs make security upgrades cheap)?
- Chosen for fit, not hype or popularity alone.
Maintenance & health
- Active development: meaningful commits and a release within the last ~12 months.
- Responsive maintainers: reasonable issue/PR turnaround.
- Bus factor > 1: multiple active maintainers, ideally from different orgs. Most popular OSS has a truck factor of 1–2 (Avelino et al., ICPC 2016) — treat a single maintainer as real risk.
- Funded/sustainable enough to keep going (sponsors, a foundation, paid maintainers).
- Real adoption: downloads and dependents (more eyes, more real-world testing).
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.
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.
- 10d ago First seen · 89 lines · 56 tokens per session scan A 4667007475ed
buy-vs-build-dependency is a skill published in the GitHub repository stdin/buy-vs-build (3 stars, last pushed 2mo ago), licensed MIT. It adds 56 tokens to every session and 1,040 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 2026-08-31.
Other skills, from other repositories
cr-next-type-llm
Cursor rules for next-type-llm.
debugging-loop
Systematic reproduce-isolate-fix-verify loop for bugs, test failures, and unexpected behavior. Use when something is broken and the cause is not yet known.
implementation-loop
Disciplined plan-build-verify loop for implementing a feature or change. Use when building something new or modifying existing behavior, especially across multiple files.
tw-migrate
Analyze a Tailwind CSS v3 project and generate a complete migration plan to v4. Scans config, CSS, and template files for v3 patterns and produces a prioritized checklist with exact find-and-replace commands.
tw-component
Generate a UI component using correct Tailwind CSS v4 utility classes, CSS variable theming, and accessibility best practices. Prevents v3 syntax hallucination by grounding output in verified v4 patterns.
docstruct
Documentation architecture discipline for AI agents. Use when creating, updating, auditing, or organizing software project documentation so docs stay clear, non-duplicated, source-of-truth driven, and token-efficient.