validation

validation is a skill for Claude Code, Codex from jkaninda/okapi-skills. It costs 0 tokens per session (2,387 once invoked), scanned A, original, MIT.

A Go request-checking system that uses tags on struct fields to describe allowed values and requirements. It also uses those rules when generating an OpenAPI description of the API.

In plain words
What is it for?
Use it to require fields, set defaults, limit numbers or text length, check patterns and formats, and restrict values to a list.
Why use it?
It keeps input checks close to the data definition and applies them automatically when requests are bound to Go values.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/jkaninda/okapi-skills/validation
Any agent
npx skills add jkaninda/okapi-skills --skill validation
Clone the repo
git clone --depth 1 https://github.com/jkaninda/okapi-skills

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.

agentmods badge for validation

README.md
[![agentmods](https://agentmods.dev/badge/skills/jkaninda/okapi-skills/validation.svg)](https://agentmods.dev/skills/jkaninda/okapi-skills/validation)
Your own site
<a href="https://agentmods.dev/skills/jkaninda/okapi-skills/validation"><img src="https://agentmods.dev/badge/skills/jkaninda/okapi-skills/validation.svg" alt="Measured on agentmods" height="20"></a>
Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,387 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.02387
Opus 5 $0.00000 $0.01193
Sonnet 5 $0.00000 $0.00477
Haiku 4.5 $0.00000 $0.00239

Measured 5d ago against content hash bd8dab55ed33, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

validation 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 5d 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.

validation/SKILL.md · 242 lines

How it starts

The opening of the file, as written. The whole thing — 242 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Okapi Validation

Validation is declarative: struct tags drive both runtime enforcement and OpenAPI schema generation. Validation runs automatically inside c.Bind and inside the typed handler wrappers (okapi.Handle, okapi.H, okapi.HandleIO, okapi.HandleO).

For where values come from (JSON body, query, path, header, cookie, form), see the request_binding/ skill.

Constraint Tags

Tag Applies to Description
required:"true" any Field must be present and non-zero
default:"v" any Assigned when the field is missing/empty
min:"5" number ≥ 5
max:"100" number ≤ 100
exclusiveMin:"0" number > 0
exclusiveMax:"100" number < 100
multipleOf:"5" number Divisible by 5
minLength:"3" string Length ≥ 3
maxLength:"50" string Length ≤ 50
pattern:"^[A-Z]+$" string / []string Regular expression
format:"email" string / []string Format validation (table below)
enum:"a,b,c" string / []string One of the listed values
const:"active" string / []string Must equal a fixed value (JSON Schema const in OAS 3.1)
contains:"@" string / []string Must contain the substring
notContains:" " string / []string Must not contain the substring
minItems:"2" slice At least 2 items
maxItems:"5" slice At most 5 items
uniqueItems:"true" slice No duplicates
minProperties:"1" map At least 1 entry
maxProperties:"10" map At most 10 entries

Slices: enum, const, format, pattern, contains, and notContains apply to each element of a []string. Failures are reported per index — element [2]: ....

Empty values: those same tags skip empty strings. Combine with required:"true" to also enforce presence.

Conditional Required Tags

Requiredness that depends on sibling fields in the same struct. Referenced fields use their Go field name, not the JSON name.

Read the full file on GitHub · 242 lines

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.

  1. 5d ago First seen · 242 lines · 0 tokens per session scan A bd8dab55ed33

Subscribe to this mod's changes

validation is a skill published in the GitHub repository jkaninda/okapi-skills (3 stars, last pushed 20d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 2,387 tokens. 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.

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