Modern Web Guidance is a source repository for coding-agent skills that provide web-platform guidance, recommended practices, and browser compatibility information. It helps coding agents choose newer web APIs and patterns when generating web applications. The catalogue skills are the guidance produced and maintained by this project.
Borrowing it
Nothing to install: this file belongs to GoogleChrome/modern-web-guidance-src. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/GoogleChrome/modern-web-guidance-src/main/.agents/skills/project-guides/SKILL.mdgit clone --depth 1 https://github.com/GoogleChrome/modern-web-guidance-srcWrote 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/googlechrome/modern-web-guidance-src/project-guides)<a href="https://agentmods.dev/skills/googlechrome/modern-web-guidance-src/project-guides"><img src="https://agentmods.dev/badge/skills/googlechrome/modern-web-guidance-src/project-guides/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/googlechrome/modern-web-guidance-src/project-guides"><img src="https://agentmods.dev/badge/skills/googlechrome/modern-web-guidance-src/project-guides.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00038 | $0.05093 |
| Opus 5.5 | $0.00015 | $0.02037 |
| Sonnet 5.5 | $0.00008 | $0.01019 |
| Haiku 4.5 | $0.00004 | $0.00509 |
Grade A, and why
project-guides 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 yesterday.
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 — 160 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Stage 2: Authoring guidance for a use case (Needs guidance)
This is the second of three stages in creating guidance:
- Stage 1: Identifying use cases for a feature
- Stage 2: Authoring guidance for a use case (you are here)
- Stage 3: Evaluating guidance for a use case
What a real-world coding agent sees
When a developer asks an AI coding assistant to implement something, the assistant retrieves the relevant guide.md via a RAG (vector search) system. guide.md is the only project file a real-world coding agent ever sees. Everything else in a use case directory is eval infrastructure:
| File/Directory | Purpose | Seen by real-world agents? |
|---|---|---|
guide.md |
Guidance for implementing the use case | ✅ Yes — this is the only file |
expectations.md |
Verification criteria used to generate target evaluation suites | ❌ No |
demo.html |
Reference implementation of the use case | ❌ No |
targets/<base_app>/solution.patch |
Golden diff against clean base app used to calibrate the grader | ❌ No |
targets/<base_app>/zero-passrate.patch |
Guidance-absent diff used to verify grader assertions fail when requirements are not implemented | ❌ No |
targets/<base_app>/grader.ts |
Playwright test suite run against the eval agent's output | ❌ No |
targets/<base_app>/task.md |
Simulated developer prompts fed to the eval agent by the harness | ❌ No |
Implication for authoring (guide.md, expectations.md, & demo.html): Authors and SMEs strictly author guide.md, expectations.md, and demo.html. You do not author solution.patch, zero-passrate.patch, grader.ts, or task.md—those evaluation files are generated separately by the eval pipeline.
Implication for guide.md: Because guide.md is the agent's only source of truth, it must be entirely self-contained. Do not rely on agents reading expectations.md, any target patch, or any external link to understand how to implement the use case.
MANDATORY RULES FOR WRITING guide.md:
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.
- yesterday Changed · +2 lines 161497be93eb
- 8d ago Changed · +19 lines · +12 tokens per session 1635fdf9d954
- 12d ago Changed · +3 lines ab998a111c6b
- 19d ago Changed 6abc053ebee9
- 21d ago Changed · +11 lines 0aedd09bf537
- 22d ago Changed · +3 lines fe3dbbb82e3c
- 23d ago Changed · +1 lines cf0385631285
- 25d ago Changed d066569989c4
- 29d ago Changed 9a4fa4032962
- 1mo ago First seen · 121 lines · 26 tokens per session scan A c7b98a2cb7c0
project-guides is a skill published in the GitHub repository GoogleChrome/modern-web-guidance-src (1,209 stars, last pushed today), licensed Apache-2.0. It adds 38 tokens to every session and 5,093 once invoked, about $0.0002 per session on Opus 5.5. 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.
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