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Agent skill

Validate In function Object() { [native code] }

by 0xMiden in 0xMiden/protocol

A skill your agent uses when writing or reviewing a Rust constructor, trynew, or builder build — centralize validation so every instance is valid by construction.

MITAuto-check passedDevelopment

Install Validate In function Object() { [native code] }

skills CLI
$ npx skills add 0xMiden/protocol --skill validate-in-constructor -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install 0xMiden/protocol validate-in-constructor --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/0xMiden/protocol.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.claude/skills/validate-in-constructor .claude/skills/validate-in-constructor && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
validate-in-constructor
GitHub stars
133
Token cost
~502 tokens
SKILL.md length
142 words
Files
1
Skills in repo
35
Repo updated
First seen
Licence
MIT

At a glance

A skill your agent uses when writing or reviewing a Rust constructor, trynew, or builder build — centralize validation so every instance is valid by construction.

  • Works in 3 steps: Validate every invariant the type… → Return Err on any input that would make… → Be the only externally callable way to…
  • Reviewing a Rust constructor
  • SKILL.md covers Rule, Why and Examples
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Validate In function Object() { [native code] } is an agent skill from 0xMiden/protocol. Use when writing or reviewing a Rust constructor, trynew, or builder build — centralize validation so every instance is valid by construction.

Its SKILL.md is about 500 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Development. It works with Rust. The repository describes itself as: Core components of the Miden protocol. The licence is MIT.

When your agent uses it

  • Reviewing a Rust constructor
  • Builder build — centralize validation so every instance is valid by construction

Example prompts

  • “/validate-in-constructor”

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

  1. Validate every invariant the type promises to uphold.
  2. Return Err on any input that would make the resulting value unusable — empty allowlists, zero thresholds, mutually inconsistent fields, etc.
  3. Be the only externally callable way to produce an instance (struct literal construction must not be possible from outside the module).

What it can do on your machine

Read from SKILL.md and the folder at commit 474c88e. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are rust).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Validate In function Object() { [native code] } loads about 502 tokens when it runs. Until then it costs about 43 tokens; SKILL.md has 142 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~43
When it runs · the whole SKILL.md, loaded when a task matches
~502

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from 0xMiden/protocol at commit 474c88e, republished under its MIT licence (© 0xMiden). 142 words, ~502 tokens.

Download SKILL.mdSave it as .claude/skills/validate-in-constructor/SKILL.md (or your agent's skills folder).
name
validate-in-constructor
description
Use when writing or reviewing a Rust constructor, `try_new`, or builder `build` — centralize validation so every instance is valid by construction.

Validate Invariants in Constructors

Rule

Every fallible construction path for a struct must run all invariants in a single canonical constructor (or builder build). The constructor must:

  1. Validate every invariant the type promises to uphold.
  2. Return Err on any input that would make the resulting value unusable — empty allowlists, zero thresholds, mutually inconsistent fields, etc.
  3. Be the only externally callable way to produce an instance (struct literal construction must not be possible from outside the module).

Do not split validation across the constructor and downstream methods; do not allow direct field initialization that bypasses checks.

Why

If a type can be constructed in an invalid or in-between state, every consumer has to defend against it; centralizing validation means holding a T is proof its invariants hold. Rejecting unusable configurations early keeps bugs from surfacing far from their cause.

Examples

rust
// Good: single validating constructor, no public fields
pub struct ProcedurePolicyMode {
    immediate_threshold: u32,
}

impl ProcedurePolicyMode {
    pub fn new(immediate_threshold: u32) -> Result<Self, PolicyError> {
        if immediate_threshold == 0 {
            return Err(PolicyError::ZeroThreshold);
        }
        Ok(Self { immediate_threshold })
    }
}

// Good: reject empty allowlist that would brick the account
impl ScriptRoots {
    pub fn new(roots: BTreeSet<Digest>) -> Result<Self, Error> {
        if roots.is_empty() {
            return Err(Error::EmptyAllowlist);
        }
        Ok(Self { roots })
    }
}

// Bad: in-between invalid state possible
let mut metadata = FungibleTokenMetadata::default();
metadata.set_name(name);
metadata.set_supply(supply);
metadata.validate()?;  // can be forgotten

© 0xMiden, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .claude/skills/validate-in-constructor of 0xMiden/protocol.

Open the folder on GitHubat commit 474c88e

Compare with similar skills

Validate In function Object() { [native code] } next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Validate In function Object() { [native code] } compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Validate In function Object() { [native code] } this skill0xMiden/protocol133—~502Automated safety check: PassMIT
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Rust Best Practicesfarm-fe/farm5.6k3 repos~1.1kAutomated safety check: PassMIT
OpenLogi macOS Permissions TriageAprilNEA/OpenLogi23k—~2.5kAutomated safety check: NotesApache-2.0
RTK Rust Design Patternsrtk-ai/rtk83k—~1.9kAutomated safety check: PassApache-2.0
Release Skillsnexmoe/eve4213 repos~3.3kAutomated safety check: PassNone

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Works with

Categories

Questions about Validate In function Object() { [native code] }

What does Validate In function Object() { [native code] } do?

A skill your agent uses when writing or reviewing a Rust constructor, trynew, or builder build — centralize validation so every instance is valid by construction. Validate In function Object() { [native code] } is an agent skill from 0xMiden/protocol. Use when writing or reviewing a Rust constructor, trynew, or builder build — centralize validation so every instance is valid by construction.

When should I use Validate In function Object() { [native code] }?

Validate In function Object() { [native code] } fits situations like: reviewing a Rust constructor; builder build — centralize validation so every instance is valid by construction.

How do I install Validate In function Object() { [native code] } in Claude Code?

Run `npx skills add 0xMiden/protocol --skill validate-in-constructor -a claude-code`. Or copy the skill folder (.claude/skills/validate-in-constructor in 0xMiden/protocol) into .claude/skills/validate-in-constructor in your project. Claude Code loads it when a task matches its description.

How do I install Validate In function Object() { [native code] } in Codex?

Run `npx skills add 0xMiden/protocol --skill validate-in-constructor -a codex`. Or copy the skill folder (.claude/skills/validate-in-constructor in 0xMiden/protocol) into .agents/skills/validate-in-constructor in your project. Codex loads it when a task matches its description.

Can I use Validate In function Object() { [native code] } in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add 0xMiden/protocol --skill validate-in-constructor -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/validate-in-constructor, .gemini/skills/validate-in-constructor, .github/skills/validate-in-constructor and .opencode/skills/validate-in-constructor in your project.

What does Validate In function Object() { [native code] } need to run?

SKILL.md names no scripts, command-line tools or credentials: Validate In function Object() { [native code] } is instructions for the agent only.

Does Validate In function Object() { [native code] } access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Validate In function Object() { [native code] } safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Validate In function Object() { [native code] } use?

Validate In function Object() { [native code] } is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Validate In function Object() { [native code] } use?

About 502 tokens (SKILL.md is roughly 2k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Validate In function Object() { [native code] }?

Skills that share tags, products or a category with Validate In function Object() { [native code] }: Migrate Core Code to Submodules (tinyhumansai/openhuman, 42k stars), Rust Best Practices (farm-fe/farm, 5.6k stars), OpenLogi macOS Permissions Triage (AprilNEA/OpenLogi, 23k stars) and RTK Rust Design Patterns (rtk-ai/rtk, 83k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Validate In function Object() { [native code] }?

0xMiden (a GitHub organization) maintains it in 0xMiden/protocol, which has 133 GitHub stars. The repository holds 35 skills in this directory. The repository was last updated on October 7, 2026.

Source: 0xMiden/protocol on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.