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.
npx skills add cyanxxy/nl-tax-agent-skills --skill nl-tax-box3git clone --depth 1 https://github.com/cyanxxy/nl-tax-agent-skillsWrote 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/cyanxxy/nl-tax-agent-skills/nl-tax-box3)<a href="https://agentmods.dev/skills/cyanxxy/nl-tax-agent-skills/nl-tax-box3"><img src="https://agentmods.dev/badge/skills/cyanxxy/nl-tax-agent-skills/nl-tax-box3/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/cyanxxy/nl-tax-agent-skills/nl-tax-box3"><img src="https://agentmods.dev/badge/skills/cyanxxy/nl-tax-agent-skills/nl-tax-box3.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00043 | $0.01699 |
| Opus 5.5 | $0.00017 | $0.00680 |
| Sonnet 5.5 | $0.00009 | $0.00340 |
| Haiku 4.5 | $0.00004 | $0.00170 |
Grade A, and why
nl-tax-box3 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 11d 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.
How it starts
The opening of the file, as written. The whole thing — 138 lines — stays where its author put it; the contents beside it link to each section on GitHub.
NL Tax Box 3
Background helper for Box 3 findings. It returns asset classification, arithmetic, and open questions to the owning annual or provisional workflow.
Boundaries that always apply
- Provisional 2026 is fictitious-only. Never collect, calculate, or ask for werkelijk rendement in a provisional workflow. If the user asks, say: "Werkelijk rendement may become relevant when filing the annual 2026 return in 2027." Annual 2025 covers the fictitious return and, for user review, the werkelijk-rendement comparison.
- Writes nothing. Return structured facts and open questions to the owning workflow. Do not persist anything: no file, workpack section, field map, or checklist. The owning workflow decides what enters its workpack.
- Authenticated-portal boundary. Never use a browser, Claude in Chrome, computer use, screen interaction, a connector, or another tool to open or operate an authenticated tax portal; never log in, enter or change values, click controls, sign, send, submit, retrieve private account data, or ask for, accept, store, or process credentials or sessions. Those actions remain human-only even with taxpayer permission or available credentials.
- Annual and provisional stay separate. Peildatum 1 January 2025 facts belong to annual 2025; 1 January 2026 estimates belong to provisional 2026. Never carry an annual amount into a provisional estimate without the taxpayer reviewing it as a 2026 estimate.
- No identifiers. Never record a BSN, IBAN, full account number, policy, contract, or aanslag number, or a credential, from a document or the chat; a provider name plus tax year identifies a document.
This helper participates in a conversational workflow. It does not assume all asset and debt inputs are pre-staged. When values are missing, return a structured open-question packet for the owning workflow instead of inventing zeros.
This helper may be called through a Skill/Task tool or inlined by an owning workflow when no such tool exists. The same output contract applies either way.
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.
- 11d ago Changed · +1 lines 655d9b37ceec
- 1mo ago Changed · +22 lines 3d8233c3faf9
- 1mo ago Changed · -2 lines 6432cb9853e5
- 1mo ago Changed b75df24cf823
- 1mo ago First seen · 117 lines · 43 tokens per session scan A 6403a2e75bf6
nl-tax-box3 is a skill published in the GitHub repository cyanxxy/nl-tax-agent-skills (10 stars, last pushed 11d ago), licensed Apache-2.0. It adds 43 tokens to every session and 1,699 once invoked, about $0.0002 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 2026-08-31.
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