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 skills add Casper-Studios/casper-marketplace --skill valibot-best-practicesgit clone --depth 1 https://github.com/Casper-Studios/casper-marketplaceWrote 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/casper-studios/casper-marketplace/valibot-best-practices)<a href="https://agentmods.dev/skills/casper-studios/casper-marketplace/valibot-best-practices"><img src="https://agentmods.dev/badge/skills/casper-studios/casper-marketplace/valibot-best-practices/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/casper-studios/casper-marketplace/valibot-best-practices"><img src="https://agentmods.dev/badge/skills/casper-studios/casper-marketplace/valibot-best-practices.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00040 | $0.00545 |
| Opus 5 | $0.00020 | $0.00272 |
| Sonnet 5 | $0.00008 | $0.00109 |
| Haiku 4.5 | $0.00004 | $0.00055 |
Grade A, and why
valibot-best-practices 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 6d 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 — 38 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Valibot Best Practices
Treat a Valibot schema as the owned contract at an untrusted data boundary: it defines accepted wire values, produces trusted domain values, and makes invalid input an explicit, intentional outcome.
Library Sources
- GitHub repository ID:
open-circle/valibot - Context7 library ID:
/open-circle/valibot - DeepWiki repository ID:
open-circle/valibot
Use Context7 for current documentation and DeepWiki for implementation details.
Effective Strategies for Valibot
Read the references that apply to the current task before defining or reviewing Valibot schemas and parsing code.
- Make schemas the owned, trusted contract for wire data.
- Make a schema that proves a domain shape the single source of truth and infer the exported type instead of maintaining a duplicate declaration.
- Validate serialized data at its trust boundary, including authenticated external payloads, before it becomes a domain value.
- Keep constructors under the
vnamespace so library ownership stays clear and import forms remain consistent.
- Encode exact wire semantics inside the schema.
- Encode missing and
nullwire semantics with the matching wrapper rather than whichever wrapper compiles. - Dispatch literal-tagged alternatives with
v.variantso Valibot selects and reports the failing tagged branch. - Define defaults with exact domain meaning in the schema; do not use a default to reinterpret malformed input.
- Transform normalized wire input inside the schema so consumers receive trusted domain values rather than raw serialized forms.
- Encode missing and
- Make validation failure match the boundary contract.
- Choose the parse API from the failure contract: abort a violated invariant or return an expected validation branch.
- Preserve expected validation issues instead of substituting an invented
nullor empty value.
What ships with it
11 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.
- agents/openai.yaml 121 B
- LICENSE.txt 16 KB
- references/discriminated-variants.md 858 B
- references/namespace-imports.md 381 B
- references/parse-failure-contracts.md 697 B
- references/schema-defaults.md 292 B
- references/schema-ownership.md 562 B
- references/schema-transformations.md 212 B
- references/serialized-trust-boundaries.md 670 B
- references/validation-failure-preservation.md 565 B
- references/wire-nullability.md 723 B
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.
- 6d ago Changed · +3 lines · -30 tokens per session 35c7a65e219b
- 11d ago First seen · 35 lines · 70 tokens per session scan A eb27507eaac0
valibot-best-practices is a skill published in the GitHub repository Casper-Studios/casper-marketplace (12 stars, last pushed 6d ago), licensed MPL-2.0. It adds 40 tokens to every session and 545 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 2026-08-30.
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