typescript-eval

typescript-eval is a skill for Claude Code, Codex from vellum-ai/vellum-assistant. It costs 14 tokens per session (430 once invoked), scanned C, original, MIT.

A guide for running TypeScript code snippets before saving them as managed skills. TypeScript is a programming language that adds type checking to JavaScript.

In plain words
What is it for?
Use it to evaluate and verify TypeScript skill code during development.
Why use it?
It catches errors in a snippet before the code becomes a reusable skill. It also supports testing functions with sample input.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to evaluate and verify TypeScript skill code during development.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/vellum-ai/vellum-assistant/typescript-eval
About the project

Vellum Assistant is a personal AI assistant that remembers information about users, learns their preferences, and takes actions across connected apps. It is intended for people who want an assistant that can manage conversations, unfinished work, and proactive notifications over time. The catalogue skills, hooks, instruction, and setting configure or extend how the assistant works.

vellum-ai/vellum-assistant · 1,201 stars · on GitHub · vellum.ai

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 vellum-ai/vellum-assistant --skill typescript-eval
Clone the repo
git clone --depth 1 https://github.com/vellum-ai/vellum-assistant

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 typescript-eval

README.md
[![agentmods](https://agentmods.dev/badge/skills/vellum-ai/vellum-assistant/typescript-eval.svg)](https://agentmods.dev/skills/vellum-ai/vellum-assistant/typescript-eval)
Your own site
<a href="https://agentmods.dev/skills/vellum-ai/vellum-assistant/typescript-eval"><img src="https://agentmods.dev/badge/skills/vellum-ai/vellum-assistant/typescript-eval.svg" alt="Measured on agentmods" height="20"></a>
Per session 14 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 430 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 2 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Tool Misuse · line 55
    Tool parameters are crafted to achieve unintended or unsafe behavior. Parameter abuse can bypass intended safety checks (e.g. shell=True, --force, dangerous glob patterns).
    Fix: Validate all tool parameters against an allowlist. Reject dangerous parameter values (shell=True, --force, -rf /) and use safe defaults.
  • high Tool Misuse · line 55
    Tool parameters are crafted to achieve unintended or unsafe behavior. Parameter abuse can bypass intended safety checks (e.g. shell=True, --force, dangerous glob patterns).
    Fix: Validate all tool parameters against an allowlist. Reject dangerous parameter values (shell=True, --force, -rf /) and use safe defaults.
How audits are shown
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 5.1 $0.00014 $0.00430
Opus 5 $0.00007 $0.00215
Sonnet 5 $0.00003 $0.00086
Haiku 4.5 $0.00001 $0.00043

Measured 4d ago against content hash fd5a1e8c4546, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade C, and why

typescript-eval scanned grade C with 1 finding 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 4d 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.

Recursive force deletehighDestructive command

rm -rf with a variable or a broad path is one typo away from removing the wrong tree.

bash command="rm -rf /tmp/vellum-eval/"
skills/typescript-eval/SKILL.md · 64 lines

What it actually says

TypeScript Evaluation

When you need to test a TypeScript snippet before persisting it as a managed skill, use bash directly.

Workflow

1. Write the snippet to a temp file

bash command="mkdir -p /tmp/vellum-eval && cat > /tmp/vellum-eval/snippet.ts << 'SNIPPET_EOF'
<your code here>
SNIPPET_EOF"

2. Run it with bun

bash command="bun run /tmp/vellum-eval/snippet.ts" timeout_seconds=10

3. For function-based testing

If the snippet exports a default or run function, write a runner script:

bash command="cat > /tmp/vellum-eval/runner.ts << 'RUNNER_EOF'
import * as mod from './snippet.ts';
const fn = (mod as any).default ?? (mod as any).run;
const input = {}; // mock input
const result = await fn(input);
console.log(JSON.stringify(result, null, 2));
RUNNER_EOF"

Then run the runner:

bash command="bun run /tmp/vellum-eval/runner.ts" timeout_seconds=10

4. Clean up

bash command="rm -rf /tmp/vellum-eval/"

Guidelines

  • Iteration limit: Max 3 attempts before asking the user for guidance.
  • After successful test: Persist with scaffold_managed_skill only after explicit user consent.
  • Timeout: Use timeout_seconds=10 (or up to 20 for complex snippets).
  • Never persist or delete skills without explicit user confirmation.
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. 4d ago Changed · -1 lines fd5a1e8c4546
  2. 4d ago First seen · 65 lines · 14 tokens per session scan C d2cabfb07bbc

Subscribe to this mod's changes

typescript-eval is a skill published in the GitHub repository vellum-ai/vellum-assistant (1,201 stars, last pushed yesterday), licensed MIT. It adds 14 tokens to every session and 430 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it C with 1 finding (recursive force delete). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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