Instructions for using a Biome MCP server to check, lint, and format TypeScript and web projects. Biome is a code-quality tool, and these checks report problems without editing files or managing dependencies.

Use it after changing TypeScript or web code to run Biome checks, inspect diagnostics, and verify formatting on changed or selected files.

It provides a consistent way to verify code quality and formatting while keeping the checks read-only.

biome — Skill for Claude Code and Codex by yriveiro

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add yriveiro/biome-mcp --skill biome

Clone the repo

git clone --depth 1 https://github.com/yriveiro/biome-mcp

Made for: Claude Code, Codex.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/yriveiro/biome-mcp/biome/github.svg)](https://agentmods.dev/skills/yriveiro/biome-mcp/biome)

Your own site

<a href="https://agentmods.dev/skills/yriveiro/biome-mcp/biome"><img src="https://agentmods.dev/badge/skills/yriveiro/biome-mcp/biome/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/yriveiro/biome-mcp/biome"><img src="https://agentmods.dev/badge/skills/yriveiro/biome-mcp/biome.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 45 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 546 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

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	$0.00045	$0.00546
Opus 5	$0.00023	$0.00273
Sonnet 5	$0.00009	$0.00109
Haiku 4.5	$0.00005	$0.00055

Measured 9d ago against content hash 98f675cb8acd, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

biome 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 9d 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.

src/biome_mcp/skills/biome/SKILL.md · 58 lines

What it actually says

biome Skill

biome-mcp exposes compact, read-only quality checks for TypeScript and web projects. It does not modify source files or manage JavaScript dependencies.

Tools

Need	Tool	Arguments
Run all Biome checks	`biome_check`	`paths?: list[str]`, `changed_only?: bool`
Run lint checks	`biome_lint`	`paths?: list[str]`, `level?: "all"
Verify formatting	`biome_format`	`paths?: list[str]`, `changed_only?: bool`

Use these MCP tools instead of shelling out to Biome when they are in the tool context. Their output is structured and intentionally compact.

Fast Feedback

After changing TypeScript or web code:

Run biome_check(changed_only=true).
Run biome_format(changed_only=true).
Fix the reported files and rerun the affected check.

Use biome_lint(level="all", changed_only=true) when informational diagnostics are relevant. Always inspect the returned exit_code.

Target Selection

Omit paths to check the whole project.
Pass files, directories, or glob patterns such as paths=["src/**/*.ts"].
Use changed_only=true for staged, unstaged, and untracked web files in the current Git repository. It takes precedence over paths.
When no modified web files exist, a changed-only check succeeds with No modified web files found.

Documentation

Use search_documentation for Biome CLI, configuration, and JavaScript linter questions. Read the returned biome:docs:// resources for detailed content.

References

Full tool catalog with signatures: references/MCP-TOOLS.md
Installing Biome, configuring the server, targeting checks: references/PROJECT-SETUP.md
Error handling and where to look up docs: references/TROUBLESHOOTING.md

Files

What ships with it

3 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.

Changes

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.

9d ago First seen · 58 lines · 45 tokens per session scan A 98f675cb8acd

Subscribe to this mod's changes

biome is a skill published in the GitHub repository yriveiro/biome-mcp (0 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 45 tokens to every session and 546 once invoked, about $0.0002 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.

Debugging

debug-optimize-lcp

Guides debugging and optimizing Largest Contentful Paint (LCP) using Chrome DevTools MCP tools. Use this skill whenever the user asks about LCP performance, slow page loads, Core Web Vitals optimization, or wants to understand why their page's main content takes too long to appear. Also use when the user mentions…

ChromeDevTools/chrome-devtools-mcp · 99 tokens

systematic-debugging

Use when debugging a failing test, build error, or runtime issue that isn't immediately obvious. Guides a 4-phase root cause analysis instead of random fix attempts.

open-metadata/OpenMetadata · 37 tokens

diagnose

Trace from a reproduced symptom to the source code that causes it. Pin the specific file and approximate line, rate confidence in the cause and clarity of the fix independently, and always propose a concrete fix.

emdash-cms/emdash · 43 tokens

repro-admin

Reproduce an EmDash admin UI bug. Attach a container, start the demo dev server, drive the admin with agent-browser using the dev-bypass session, and capture the reproduction as screenshots plus a replayable transcript.

emdash-cms/emdash · 48 tokens

log-error-digest

Analyze log files to troubleshoot errors, identify peak error periods, and produce error clustering, frequency statistics, and time distribution reports. Supports JSON, syslog, and Nginx formats with automatic detection. Use when a user uploads a .log file and asks to analyze errors, find patterns, debug issues, or…

zebbern/claude-code-guide · 71 tokens

byted-util-volcengine-detect-retry

An orchestration workflow for Volcengine Cloud Detect, a service that checks websites or network endpoints from test locations.

bytedance/agentkit-samples · 101 tokens