What is Validating Inputs?

A coding practice for checking data received from outside the program before using it. External inputs include user entries, files, network requests, and other systems.

Use it for request data, configuration, file contents, command-line arguments, and service responses. It helps verify required fields, types, ranges, and allowed values.

Invalid input can cause incorrect results, crashes, or unsafe behavior. Checking it at the boundary prevents bad data from spreading through the program.

Validating Inputs — Skill for Claude Code by obra/clank

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 obra/clank --skill validating-inputs

Clone the repo

git clone --depth 1 https://github.com/obra/clank

Made for: Claude Code.

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/obra/clank/validating-inputs/github.svg)](https://agentmods.dev/skills/obra/clank/validating-inputs)

Your own site

<a href="https://agentmods.dev/skills/obra/clank/validating-inputs"><img src="https://agentmods.dev/badge/skills/obra/clank/validating-inputs/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/obra/clank/validating-inputs"><img src="https://agentmods.dev/badge/skills/obra/clank/validating-inputs.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 20 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 4,671 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 unknown 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	$0.00020	$0.04671
Opus 5.5	$0.00008	$0.01868
Sonnet 5.5	$0.00004	$0.00934
Haiku 4.5	$0.00002	$0.00467

Measured 2mo ago against content hash 7adf2fb5cac3, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

Validating Inputs 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 2mo 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.

skills/coding/validating-inputs/SKILL.md · 657 lines

The source is not reproduced here

No licence file

Read it on GitHub

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.

2mo ago First seen · 657 lines · 20 tokens per session scan A 7adf2fb5cac3

Subscribe to this mod's changes

Validating Inputs is a skill published in the GitHub repository obra/clank (43 stars, last pushed 1y ago), with no licence file. It adds 20 tokens to every session and 4,671 once invoked, about $0.0001 per session on Opus 5.5. 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.