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/nightly-eval-investigation/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/nightly-eval-investigation)<a href="https://agentmods.dev/skills/googlechrome/modern-web-guidance-src/nightly-eval-investigation"><img src="https://agentmods.dev/badge/skills/googlechrome/modern-web-guidance-src/nightly-eval-investigation/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/nightly-eval-investigation"><img src="https://agentmods.dev/badge/skills/googlechrome/modern-web-guidance-src/nightly-eval-investigation.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 | $0.00078 | $0.03064 |
| Opus 5 | $0.00039 | $0.01532 |
| Sonnet 5 | $0.00016 | $0.00613 |
| Haiku 4.5 | $0.00008 | $0.00306 |
Grade A, and why
nightly-eval-investigation 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 11d 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 — 224 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Nightly Evaluation Investigation
This skill automates the retrieval and multi-agent comparison of remote nightly evaluation runs from Google Cloud Storage (GCS) to diagnose system-wide guidance health, task drift, and over-prescribed guides.
Core Objectives
- Cross-Agent Diagnostics: Compare results across three distinct, modern agents (Claude Code, Codex CLI, and Jetski CLI) to locate patterns that are agent-agnostic.
- Guide Discovery Audit: Catch cases where agents skip the expected guide or over-retrieve irrelevant guides.
- Health Thresholding: Flag tasks that either underperform under guidance or are too easy/over-prescriptive (meaning unguided runs already pass easily).
- Structured Reporting: Produce reliable Markdown and JSON artifacts that downstream automation can easily ingest.
[!IMPORTANT] CRITICAL CONSTRAINT - READ-ONLY INVESTIGATION ONLY This skill is strictly for diagnostics, investigation, and suggesting recommendations. The agent MUST NOT under any circumstances edit, modify, create, delete, or touch any files under the
guides/directory (including task files, guides, graders, expectations, or demos). All suggestions for fixes must be documented exclusively in the generated investigation report markdown file under the "Actionable Recommendations" section. No automated or manual code remediation should be performed.
Quick Reference: Remote Dashboard Results (GCS)
All nightly evaluation suites are automatically uploaded to Google Cloud Storage:
- GCS Bucket:
gs://guidance-evals/ - Naming Pattern:
nightly-YYYY-MM-DD_HH-MM-SS-[agent_type]/(note: legacy folders may contain an optional trailing-[ldap]suffix)
Distinct Agent Categories
We track three core agent implementations in our periodic evaluations:
- Claude Code (
claude_codeorclaude) - Codex CLI (
codex_cliorcodex) - Jetski CLI (
jetski_clioragyorjetski)
Flagging & Health Criteria
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.
- 11d ago First seen · 224 lines · 78 tokens per session scan A 1aaf9a32e7aa
nightly-eval-investigation is a skill published in the GitHub repository GoogleChrome/modern-web-guidance-src (1,026 stars, last pushed today), licensed Apache-2.0. It adds 78 tokens to every session and 3,064 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 2026-08-30.
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