Getting it into your agent
This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.
/plugin marketplace add AppsVortex/arness/plugin install arn-sparkWrote 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/appsvortex/arness/arn-spark-discover)<a href="https://agentmods.dev/skills/appsvortex/arness/arn-spark-discover"><img src="https://agentmods.dev/badge/skills/appsvortex/arness/arn-spark-discover/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/appsvortex/arness/arn-spark-discover"><img src="https://agentmods.dev/badge/skills/appsvortex/arness/arn-spark-discover.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 | $0.00127 | $0.05415 |
| Opus 5.5 | $0.00051 | $0.02166 |
| Sonnet 5.5 | $0.00025 | $0.01083 |
| Haiku 4.5 | $0.00013 | $0.00541 |
Grade A, and why
arn-spark-discover 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 today.
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 — 304 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Arness Discover
Guide a greenfield product idea from raw concept to structured product vision through iterative conversation, aided by product thinking from the arn-spark-product-strategist agent, competitive landscape research from arn-spark-market-researcher, and persona generation from arn-spark-persona-architect (greenfield agents in this plugin). This is a conversational skill that runs in normal conversation (NOT plan mode). The primary artifact is a product concept document written to the project's vision directory.
This skill covers the WHAT and WHY of the product, including the product pillars -- non-negotiable qualities that define the product's soul and guide all downstream decisions. Technology choices and system design are handled separately by /arn-spark-arch-vision.
Step 0: Ensure Configuration (Non-Blocking)
Read ${CLAUDE_PLUGIN_ROOT}/skills/arn-spark-ensure-config/references/step-0-fast-path.md and follow its instructions. This captures the user profile and configures ## Arness with Arness Spark fields.
Important: This skill is designed for exploratory use before a project may fully exist. If ensure-config encounters errors (e.g., no git repository, CLAUDE.md cannot be created), proceed anyway using fallback defaults: Vision directory = .arness/vision, Reports directory = .arness/reports. Do not hard-block.
After Step 0 completes (or falls back), determine the output directory:
- Read the project's
CLAUDE.mdand check for a## Arnesssection - If found, extract the configured Vision directory path — this is the source of truth
- If NOT found (ensure-config fell back), use
.arness/visionat the project root. - If the output directory does not exist, create it
Workflow
Step 1: Capture the Raw Idea
Accept the user's product idea in any form -- a single sentence, a paragraph, or a detailed description. If the idea was included in the trigger message, use it directly. If not, ask:
"What product or tool do you want to build? Describe it in whatever detail you have -- even a rough idea is a good starting point."
What ships with it
4 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.
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.
- today First seen · 304 lines · 127 tokens per session scan A 754b6fce54a9
arn-spark-discover is a skill published in the GitHub repository AppsVortex/arness (33 stars, last pushed today), licensed MIT. It adds 127 tokens to every session and 5,415 once invoked, about $0.0005 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 2026-10-25.
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