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Modern Web Guidance

JetBrainsOfficialCreated by Google ChromeDistributed by JetBrains

  • Skill
  • Tool integration
  • Software development
  • Apache-2.0
  • Low risk
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From the author

Search tool for modern web development best practices. MANDATORY: Execute FIRST for all HTML/CSS and clientside JS tasks. Do NOT skip — web APIs evolve rapidly and training weights contain obsolete patterns. Trigger immediately for: - UI/Layout: Modals, dialogs, popovers, Glassmorphism/backdrop-filters, anchor positioning, container queries, `:has()`, `:user-valid`. - Scroll/Motion: View Transitions, Scroll-driven animations, scroll parallax/reveals. - Performance: CWV (LCP, INP), content-visibility, Fetch Priority, image optimization. - System/APIs: Local filesystem access, WebUSB, WebSockets sync, WebAssembly widgets. - Frameworks: Adapting layout/styles in React, Vue, Angular. - General Frontend: Forms, autofill, advanced inputs, custom scrollbars, modern component states, etc. DO NOT trigger for: - Backend: Database SQL, ORMs, Express API routes. - Pipelines: CI/CD deployment, Docker, Actions. - Generic: Local scripts (Python/Go tools), ESLint, Git.
— the description by Google Chrome

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a structured way to access up-to-date web development patterns, ensuring that implementations follow modern standards rather than relying on potentially outdated training data. It covers a wide range of frontend topics including UI components, performance optimization, browser APIs, and form handling. By integrating this tool, developers can search for specific use cases and retrieve detailed, framework-agnostic guides that include browser support and fallback recommendations.

What it does

  • Searches for standardized web development patterns and best practices.
  • Retrieves detailed implementation guides for specific frontend use cases.
  • Provides guidance on browser compatibility and necessary fallbacks.
  • Helps avoid ad-hoc solutions and unnecessary dependency bloat.
  • Supports modern web features like container queries, view transitions, and performance APIs.

When to use it

  • At the beginning of any frontend feature implementation.
  • Before creating new components to check for existing standardized patterns.
  • When evaluating the browser support requirements for modern web features.
  • When needing to implement performance optimizations like LCP or content-visibility.

Advantages

  • Ensures use of current, recommended web development practices.
  • Reduces technical debt by discouraging ad-hoc implementations.
  • Provides clear guidance on handling browser compatibility and fallbacks.
  • Promotes the use of native browser capabilities over heavy external dependencies.

Usage examples

“I need to implement a modal using modern web standards. What is the best approach?”
The agent searches for modal-related guides and retrieves the recommended implementation pattern, including any necessary browser fallbacks.
“How can I optimize the loading priority of my LCP images?”
The agent searches for image optimization guides and retrieves the specific instructions for using fetch priority to improve performance.

Install

  1. Download the skill as a ZIP:

    https://mp-staging.autogineer.com/agent-skills/jetbrains/modern-web-guidance/download

  2. Unzip it into the cross-client skills folder of your project:

    mkdir -p .agents/skills && unzip modern-web-guidance.zip -d .agents/skills

Documentation by Google Chrome

Modern Web Guidance

A skill to search for specific web development use cases and retrieve their corresponding best practice guides.

When to use

Must use this skill:

  • At the start of implementing any web feature.

  • Before creating a new component, to check if a standardized pattern already exists.

  • To avoid implementing ad-hoc solutions or loading large dependencies unnecessarily.

Usage Instructions

Step 1. Search Use Cases

Search with an action-oriented query summarizing what you want to achieve using the search command. Run modern-web-guidance directly with npx.

npx -y modern-web-guidance@latest search "<query>" --skill-version 2026_05_16-c5e7870

Example Output:

[
  {
    "id": "optimize-image-priority",
    "description": "Optimize the loading priority of Largest Contentful Paint (LCP) candidate images.",
    "category": "performance",
    "featuresUsed": [ "Fetch priority" ],
    "tokenCount": 985,
    "similarity": 0.7289
  },
  {
    "id": "defer-rendering-heavy-content",
    "description": "Reduce rendering times in content-heavy web pages by deferring rendering for offscreen content.",
    "category": "performance",
    "featuresUsed": [ "content-visibility", "hidden=\"until-found\"" ],
    "tokenCount": 1250,
    "similarity": 0.6961
  }
]

Note: If search results are vague, return no matches, or show low similarity scores, run the list command to browse all guides:

npx -y modern-web-guidance@latest list
Step 2. Retrieve Best Practices

Once you have a relevant id from the search results, call this script using the retrieve command to get the full guide. You can pass multiple IDs separated by commas.

npx -y modern-web-guidance@latest retrieve "<id>"

Example Output: The markdown content of the guide describing implementation steps...

Using npx

  • IMPORTANT: on Windows, using npx may fail. Use npx.cmd ... instead.

  • Network access is required for fetching npm packages needed by the task.

  • If the npx -y modern-web-guidance… command hangs, you may be offline. Try running again in offline mode: npx --offline ….

  • The --skill-version flag is used to determine if this SKILL.md is out of date. If it is, a warning message is logged to stderr.

Guidelines

  • Always search first to find the most relevant guides.

  • These guides are usually framework-agnostic; adapt them correctly to your setup.

  • Do not hallucinate guides or ignore them; they represent the preferred local standard for the user's project.

Interpreting Browser Support & Fallbacks

  • Default Behavior: All guides assume Baseline Widely available features are safe to use without fallbacks. For features that are not Baseline widely available, you MUST follow the fallback recommendations in the guide, unless the user has specified a custom browser support policy.

  • Custom Policies: If the user has already defined explicit browser support requirements, use the browser compatibility data in the guide to determine if a fallback can be safely ignored.

    • For Baseline YYYY targets, a feature satisfies this target if its "Baseline since" date is <= YYYY.

    • Policy Examples:

      • "Do not implement feature fallbacks." (for exploratory prototypes of the cutting-edge web)

      • "Safari 17.4+" (for internal tools targeting macOS or Tauri-based desktop apps)

      • "Never recommend or implement polyfills; if a Baseline Newly Available feature is required for core functionality, provide a lightweight custom fallback or redesign the approach." (to minimize bundle size and avoid technical debt)

      • "Assume a modern execution environment where Baseline Newly Available features can be used natively, provided they are strictly feature-detected and degrade gracefully." (for progressive enhancement strategies)

  • Reactive Policy Discovery: Watch for environmental cues to suggest documenting a policy in CLAUDE.md or AGENTS.md. Suggest this if the developer:

    • Mentions building for a restricted runtime (e.g., Electron or Tauri).

    • Explicitly excludes specific targets (e.g., "we don't support Desktop Chrome").

    • Expresses hesitation about polyfill complexity, bundle size, or performance cost.

    • Questions if a feature is safe to use without fallbacks.

    No defined policy format. This is an example: **Browser Support:** Allow Newly Available features, but only adopt custom fallback code that adds <= 20 lines and does not require external dependencies.

Files

guides/webmcp/agentic-forms.md

The Declarative API transforms standard HTML <form> elements into WebMCP tools via attributes. The browser synthesizes a JSON Schema from the form inputs and handles agent interactions.

Form Attributes

  • toolname: Unique name for the tool.

  • tooldescription: Purpose of the tool.

  • toolautosubmit: (Optional) If present, the agent can submit the form without waiting for user interaction.

  • toolparamdescription: (Optional) Provides a way to define a property description within the JSON Schema.

    • Resolution Order: The browser uses toolparamdescription if present. In its absence, it uses the textContent of the associated <label> (skipping labelable descendants). If no label exists, it falls back to the aria-description.

    • Grouping (Fieldsets): To attach a description to a group of related elements (like <input type="radio"> buttons), place toolparamdescription on the nearest parent <fieldset> element so it applies to the parameter group as a whole.

Example
<form toolname="search-cars" 
      tooldescription="Perform a car make/model search" 
      toolautosubmit>
  <label for="make">Vehicle Make</label>
  <input type="text" id="make" name="make" required>
  
  <label for="model">Vehicle Model</label>
  <input type="text" id="model" name="model" toolparamdescription="e.g., 330i, F-150" required>
  
  <button type="submit">Search</button>
</form>

Handling Submissions in JavaScript

When an agent submits the form, the SubmitEvent includes agentInvoked (boolean) and respondWith(promise).

document.querySelector('form').addEventListener('submit', (event) => {
  event.preventDefault();

  // Validate the form
  const formValidationErrors = myFormIsValid();

  if (formValidationErrors.length > 0) {
    if (event.agentInvoked) {
      const errorString =
        'Validation failed: ' +
        formValidationErrors
          .map((err) => `${err.field} (${err.message})`)
          .join(', ');

      event.respondWith(Promise.resolve(errorString));
    }
    return;
  }

  const resultPromise = performAsyncSearch(new FormData(event.target));

  // Return the result directly to the agent without navigation
  if (event.agentInvoked) {
    event.respondWith(resultPromise);
  }
});

Lifecycle Events

The window emits events when agents start or stop interacting with a tool:

window.addEventListener('toolactivated', ({ toolName }) => {
  console.log(`Tool "${toolName}" was activated by the agent.`);
});

window.addEventListener('toolcancel', ({ toolName }) => {
  console.log(`Tool "${toolName}" interaction was cancelled.`);
});

Visual Feedback (CSS)

Use pseudo-classes to highlight forms when an agent interacts with them:

  • :tool-form-active: Applied to the <form> element actively used by the agent.

  • :tool-submit-active: Applied to the submit button when the browser pauses for user review (if toolautosubmit is omitted).

form:tool-form-active {
  outline: 2px dashed blue;
  background-color: rgba(0, 0, 255, 0.05);
}

button:tool-submit-active {
  outline: 2px dashed red;
  animation: pulse 2s infinite;
}

Form Suitability (When to Avoid)

The Declarative API is best for self-contained, standard forms. It is a poor choice in these scenarios:

  • Highly Dependent Fields: Forms where inputs change options or visibility based on other inputs. The synthesized schema cannot express these dependencies well.

  • Custom UI Components: Forms relying on non-standard inputs (e.g., canvas, rich text editors) that don't auto-serialize values.

  • Multi-Step Wizards: Complex workflows requiring multiple form submissions. The Imperative API or standard DOM interaction is better suited here.

When to use toolautosubmit

  • Read-Only Operations & Queries: Searches, filters, fetching details, or checking status (e.g., a car model search, searching a directory, checking stock availability).

  • Low-Risk, Reversible Actions: Form actions that can easily be undone or refined by the user manually (e.g., adding items to a cart, applying a coupon code, saving a draft, or setting temporary layout options).

When to omit toolautosubmit

  • Destructive or Irreversible Actions: Deleting records, resetting system configurations, or clearing databases.

  • Financial & Transactional Actions: Submitting a checkout form, transferring funds, authorizing subscription payments, or final order placements.

  • High-Impact User Communication: Submitting a final job application, sending emails/messages to other real users, or publishing public-facing content.

  • Sensitive Account Settings: Changing passwords, modifying user roles/permissions, or updating billing/profile info.

Fallback strategies

Form-associated WebMCP attributes is not natively supported by any major browser yet.

The WebMCP Declarative API is safe to use in all browsers. Browsers that do not support WebMCP will ignore the tool* attributes, and the <form> will continue to function as a normal HTML form. No feature detection is required.

Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs Node.js

Security

What our scanner noticed· Low risk

  • Instructions that use the network

A static scan is not a guarantee. Skills are third-party content: review a skill before you let an agent use it.

Attribution and licence

Created by
Google Chrome
Publisher
JetBrains (Official)
Distributed by
JetBrains
Source
JetBrains/skills · modern-web-guidance · commit 3f53782
Licence
Apache License 2.0 (redistribution allowed)
  • ATTRIBUTION.md (written by AutoGineer)
Synced

AutoGineer is not affiliated with or endorsed by Google Chrome or JetBrains.

Download ZIP

The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download modern-web-guidance.zip