Zod
jasonjgardner/blockbench-mcp-plugin
Zod schema validation best practices for type safety, parsing, and error handling.
A skill your agent uses when reviewing code that calls fetch(), reads from localStorage, accesses process.env, or processes form submissions without explicitly validating the incoming data shape.
Install Runtime Validation
$ npx skills add thedaviddias/Front-End-Checklist --skill runtime-validation -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install thedaviddias/Front-End-Checklist runtime-validation --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/runtime-validation .claude/skills/runtime-validation && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "runtime-validation" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/runtime-validation into .claude/skills/runtime-validation/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "runtime-validation", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/runtime-validationType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add thedaviddias/Front-End-Checklist --skill runtime-validation -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install thedaviddias/Front-End-Checklist runtime-validation --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/runtime-validation .agents/skills/runtime-validation && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "runtime-validation" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/runtime-validation into .agents/skills/runtime-validation/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "runtime-validation", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add thedaviddias/Front-End-Checklist --skill runtime-validation -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install thedaviddias/Front-End-Checklist runtime-validation --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/runtime-validation .cursor/skills/runtime-validation && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "runtime-validation" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/runtime-validation into .cursor/skills/runtime-validation/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "runtime-validation", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/thedaviddias/Front-End-Checklist.git --path skills/runtime-validation--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add thedaviddias/Front-End-Checklist --skill runtime-validation -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install thedaviddias/Front-End-Checklist runtime-validation --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/runtime-validation .gemini/skills/runtime-validation && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "runtime-validation" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/runtime-validation into .gemini/skills/runtime-validation/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "runtime-validation", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install thedaviddias/Front-End-Checklist runtime-validationInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add thedaviddias/Front-End-Checklist --skill runtime-validation -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/runtime-validation .github/skills/runtime-validation && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "runtime-validation" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/runtime-validation into .github/skills/runtime-validation/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "runtime-validation", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add thedaviddias/Front-End-Checklist --skill runtime-validation -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install thedaviddias/Front-End-Checklist runtime-validation --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/runtime-validation .opencode/skills/runtime-validation && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "runtime-validation" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/runtime-validation into .opencode/skills/runtime-validation/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "runtime-validation", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
runtime-validation- GitHub stars
- 74k
- Token cost
- ~585 tokens
- SKILL.md length
- 269 words
- Files
- 2 (incl. references)
- Skills in repo
- 390
- Repo updated
- First seen
- Licence
- MIT
At a glance
A skill your agent uses when reviewing code that calls fetch(), reads from localStorage, accesses process.env, or processes form submissions without explicitly validating the incoming data shape.
- Reviewing code that calls fetch()
- SKILL.md covers Quick Reference, Check, Fix and Explain, plus 1 more section
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
- Reads from localStorage
What it does
Runtime Validation is an agent skill from thedaviddias/Front-End-Checklist. Use when reviewing code that calls fetch(), reads from localStorage, accesses process.env, or processes form submissions without explicitly validating the incoming data shape.
Its SKILL.md is about 590 tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/rule.md`).
It sits in Development. It works with Zod. The repository describes itself as: 🗂 The essential checklist for modern web development, for humans and AI agents. The licence is MIT.
When your agent uses it
- Reviewing code that calls fetch()
- Reads from localStorage
- Accesses process.env
- Processes form submissions without explicitly validating the incoming data shape
Example prompts
- “/runtime-validation”
What it can do on your machine
Read from SKILL.md and the folder at commit e8d14d0. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
Links to these hosts (documentation or services it may open):
frontendchecklist.io
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Runtime Validation loads about 585 tokens when it runs, and up to ~2.5k if it reads all its reference files. Until then it costs about 49 tokens; SKILL.md has 269 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from thedaviddias/Front-End-Checklist at commit e8d14d0, republished under its MIT licence (© thedaviddias). 269 words, ~585 tokens.
Download SKILL.mdSave it as
.claude/skills/runtime-validation/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.- name
- runtime-validation
- description
- Use when reviewing code that calls fetch(), reads from localStorage, accesses process.env, or processes form submissions without explicitly validating the incoming data shape.
- metadata.category
- javascript
- metadata.priority
- high
- metadata.difficulty
- intermediate
- metadata.estimatedTime
- 30
- metadata.source
- frontendchecklist.io
- metadata.url
- https://frontendchecklist.io/rules/javascript/runtime-validation
Validate external data at runtime with a schema library
TypeScript gives you confidence at compile time, but data from the network, user input, and storage arrives at runtime as raw, untyped values. A backend schema change, a misconfigured API, or malicious input can produce data that does not match your TypeScript types — and the compiler will never warn you. Runtime validation with a schema library catches these mismatches at the boundary, surfaces clear error messages, and prevents type-unsafe data from propagating through your application.
Quick Reference
- TypeScript types are compile-time only — they are completely erased at runtime
- API responses can differ from their declared types without causing a compile error
- A Zod schema simultaneously validates data and infers the TypeScript type
- Validate at trust boundaries only — not inside every internal function call
Check
Identify all places in this code where external data enters the application (fetch calls, localStorage reads, env variable access, form submissions) and report which ones lack runtime schema validation.
Fix
Add Zod schemas to validate the external data entry points in this code. Show the schema definition, the validated type inference, and where to call .parse() or .safeParse().
Explain
Explain why TypeScript types do not protect against runtime data mismatches, how Zod bridges compile-time and runtime safety, and when to use .parse() versus .safeParse().
Code Review
Review all external data entry points in this file: API calls, storage reads, environment variable access, and form handling. Flag any location where data is cast to a TypeScript type without a preceding runtime validation step.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/rules/javascript/runtime-validation
© thedaviddias, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 1 other file (references) in skills/runtime-validation of thedaviddias/Front-End-Checklist.
- SKILL.md
- references/rule.md
Open the folder on GitHubat commit e8d14d0
Compare with similar skills
Runtime Validation next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Runtime Validation this skillthedaviddias/Front-End-Checklist | 74k | — | ~585 | Automated safety check: Pass | MIT | |
| Zodjasonjgardner/blockbench-mcp-plugin | 488 | 3 repos | ~1.4k | Automated safety check: Pass | GPL-3.0 | |
| Figma Typings Auditawdr74100/figwright | 977 | — | ~3.3k | Automated safety check: Pass | MIT | |
| Typescript Styletjx666/vscode-mcp | 106 | — | ~961 | Automated safety check: Pass | Custom licence | |
| Typed Service Contractsgoogle-labs-code/stitch-sdk | 1.8k | — | ~1.4k | Automated safety check: Pass | Apache-2.0 | |
| Add Server Env Var for User Settinglobehub/lobehub | 83k | — | ~644 | Automated safety check: Pass | Custom licence |
Similar skills
Figma Typings Audit
awdr74100/figwright
Upgrade @figma/plugin-typings and absorb what the new version exposes.
Typescript Style
tjx666/vscode-mcp
TypeScript code style and repo conventions for VSCode MCP — inference vs explicit types, ESM import suffixes, zod schema contracts, async VSCode/Node APIs, JSON-safe IPC results, JSDoc for public…
- Official
Typed Service Contracts
google-labs-code/stitch-sdk
Architecture standard for building robust, type-safe TypeScript services using the "Spec and Handler" pattern.
Add Server Env Var for User Setting
lobehub/lobehub
Adds a server-side environment variable that sets the default for a user setting in LobeHub, wired from the env schema through server config to the user store and docs.
Ban Type Assertions
Factory-AI/factory-plugins
Ban as type assertions in a package via the @typescript-eslint/consistent-type-assertions lint rule, replacing them with compiler-verified type-safe alternatives.
More from thedaviddias/Front-End-Checklist
All 390 skills in this repoContent Dates Audit
thedaviddias/Front-End-Checklist
Audits article and blog pages for visible publish dates, Article JSON-LD with datePublished and dateModified, and Open Graph time tags, then fixes what is missing.
FAQPage Schema Markup
thedaviddias/Front-End-Checklist
Adds, checks and fixes FAQPage JSON-LD on pages with visible question-and-answer sections so it matches what readers see and can qualify for rich results.
Favicon Audit and Setup
thedaviddias/Front-End-Checklist
Checks that a site's favicon is linked, reachable and large enough for Google search results, and sets up ICO, SVG and Apple touch icon files when they are missing.
Content Freshness Signals
thedaviddias/Front-End-Checklist
Audits article pages for freshness signals, covering the Last-Modified header, Article JSON-LD dateModified and a visible last-updated date, and fixes mismatches.
Geo Meta Tags Audit
thedaviddias/Front-End-Checklist
Audits and fixes geo.region, geo.placename and geo.position meta tags on regional pages, noting where they help (Bing) and where they do not (Google).
Improve a Front-End Checklist Rule
thedaviddias/Front-End-Checklist
Scores and rewrites a Front-End Checklist rule MDX file against a scored quality rubric, replacing generic stub prompts with specific, actionable ones.
Related
Works with
Categories
Questions about Runtime Validation
What does Runtime Validation do?
A skill your agent uses when reviewing code that calls fetch(), reads from localStorage, accesses process.env, or processes form submissions without explicitly validating the incoming data shape. Runtime Validation is an agent skill from thedaviddias/Front-End-Checklist.env, or processes form submissions without explicitly validating the incoming data shape.
When should I use Runtime Validation?
Runtime Validation fits situations like: reviewing code that calls fetch(); reads from localStorage; accesses process.env; processes form submissions without explicitly validating the incoming data shape.
How do I install Runtime Validation in Claude Code?
Run `npx skills add thedaviddias/Front-End-Checklist --skill runtime-validation -a claude-code`. Or copy the skill folder (skills/runtime-validation in thedaviddias/Front-End-Checklist) into .claude/skills/runtime-validation in your project. Claude Code loads it when a task matches its description.
How do I install Runtime Validation in Codex?
Run `npx skills add thedaviddias/Front-End-Checklist --skill runtime-validation -a codex`. Or copy the skill folder (skills/runtime-validation in thedaviddias/Front-End-Checklist) into .agents/skills/runtime-validation in your project. Codex loads it when a task matches its description.
Can I use Runtime Validation in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add thedaviddias/Front-End-Checklist --skill runtime-validation -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/runtime-validation, .gemini/skills/runtime-validation, .github/skills/runtime-validation and .opencode/skills/runtime-validation in your project.
What does Runtime Validation need to run?
SKILL.md names no scripts, command-line tools or credentials: Runtime Validation is instructions for the agent only.
Does Runtime Validation access the network?
SKILL.md names 1 domain. As links in the text: frontendchecklist.io. This is read from the text; nothing was executed.
Is Runtime Validation safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Runtime Validation use?
Runtime Validation is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Runtime Validation use?
About 585 tokens (SKILL.md is roughly 2.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 1.9k tokens, read only when the agent opens those files.
What are the alternatives to Runtime Validation?
Skills that share tags, products or a category with Runtime Validation: Zod (jasonjgardner/blockbench-mcp-plugin, 488 stars), Figma Typings Audit (awdr74100/figwright, 977 stars), Typescript Style (tjx666/vscode-mcp, 106 stars) and Typed Service Contracts (google-labs-code/stitch-sdk, 1.8k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Runtime Validation?
thedaviddias (a GitHub user) maintains it in thedaviddias/Front-End-Checklist, which has 74,388 GitHub stars. The repository holds 390 skills in this directory. The repository was last updated on October 6, 2026.
Source: thedaviddias/Front-End-Checklist on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.