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.
npx agentmods add skills/biomejs/biome/diagnostics-developmentnpx skills add biomejs/biome --skill diagnostics-developmentgit clone --depth 1 https://github.com/biomejs/biomeWrote 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/biomejs/biome/diagnostics-development)<a href="https://agentmods.dev/skills/biomejs/biome/diagnostics-development"><img src="https://agentmods.dev/badge/skills/biomejs/biome/diagnostics-development.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00055 | $0.00941 |
| Opus 5 | $0.00028 | $0.00470 |
| Sonnet 5 | $0.00011 | $0.00188 |
| Haiku 4.5 | $0.00006 | $0.00094 |
Grade A, and why
diagnostics-development 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 3d 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 — 102 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Diagnostics Development
Use crates/biome_diagnostics/CONTRIBUTING.md as the canonical API and design guide. Inspect current diagnostics in the same subsystem before choosing an advice type or derive shape.
Choose the Diagnostic API
Use RuleDiagnostic for lint and assist rules. Use a standalone type deriving Diagnostic when a parser, service, CLI, configuration, or infrastructure boundary needs its own structured diagnostic.
Do not introduce a standalone type solely to wrap a one-line lint message. Do not force a complex diagnostic with locations, sub-diagnostics, or conditional advice into a RuleDiagnostic chain when an owned type expresses the contract more clearly.
Three Questions
A complete diagnostic answers:
- What condition was found?
- Why does it matter?
- What can the user do?
Keep those jobs separate:
- the primary message identifies the condition;
- a note or detail explains the consequence or rationale;
- an action, diff, command, or final advice gives the next step.
Do not combine rationale and remediation into vague prose. When an automated action exists, its label normally carries the remediation rather than repeating it in a note.
Messages and Markup
- Name the actual problem, not only the syntax construct.
- Highlight the smallest source range that helps the user understand it.
- Interpolate values directly in
markup!; do not allocate withformat!first. - Use emphasis for source terms or configuration values where it improves scanning.
- Keep the primary message short; put explanation in advice.
- Do not claim a consequence the implementation does not establish.
Advice Selection
Choose advice based on the information users need:
| Need | Mechanism |
|---|---|
| Explanation or next step | note or log advice |
| Point to a related source span | detail or code-frame advice |
| Show an exact textual change | diff advice or code action |
| Show a command to run | command advice |
| Extra opt-in context | verbose advice |
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.
- 3d ago First seen · 102 lines · 55 tokens per session scan A d38007117f05
diagnostics-development is a skill published in the GitHub repository biomejs/biome (25,686 stars, last pushed 3d ago), licensed Apache-2.0. It adds 55 tokens to every session and 941 once invoked, about $0.0003 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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