nl-tax-box3

nl-tax-box3 is a skill for Claude Code, Codex from cyanxxy/nl-tax-agent-skills. It costs 43 tokens per session (1,548 once invoked), scanned A, original, Apache-2.0.

A helper for collecting Box 3 information in Dutch tax workflows. Box 3 is the Dutch tax category for savings, investments, and some debts, with different calculation rules for annual 2025 and provisional 2026 returns.

In plain words
What is it for?
It helps gather applicable savings, investment, and debt facts, identify unanswered questions, and prepare Box 3 notes for annual 2025 or provisional 2026 work.
Why use it?
It prevents the workflow from asking for irrelevant figures or inventing missing values. It also separates the 2025 comparison with actual returns from the 2026 provisional calculation.

Skill for Claude CodeCodex

Written for Claude Code and Codex: allowed-tools in frontmatter, but also agents/openai.yaml present.

Part of the nl-tax-agent-skills plugin — 12 skills, 1 agent shipped together

Good fit It helps gather applicable savings, investment, and debt facts, identify unanswered questions, and prepare Box 3 notes for annual 2025 or provisional 2026 work.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/cyanxxy/nl-tax-agent-skills/nl-tax-box3
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 cyanxxy/nl-tax-agent-skills --skill nl-tax-box3
Clone the repo
git clone --depth 1 https://github.com/cyanxxy/nl-tax-agent-skills

Made for: Claude Code, Codex.

Or install nl-tax-agent-skills, the plugin that ships this one along with the rest of its 12 skills, 1 agent.

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 nl-tax-box3

README.md
[![agentmods](https://agentmods.dev/badge/skills/cyanxxy/nl-tax-agent-skills/nl-tax-box3/github.svg)](https://agentmods.dev/skills/cyanxxy/nl-tax-agent-skills/nl-tax-box3)
Your own site
<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.

agentmods 80×15 button for nl-tax-box3

Your own site · 80×15
<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>
Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,548 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. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
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 $0.00043 $0.01548
Opus 5 $0.00022 $0.00774
Sonnet 5 $0.00009 $0.00310
Haiku 4.5 $0.00004 $0.00155

Measured 12d ago against content hash 6403a2e75bf6, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

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 12d ago.

The scan reads SKILL.md. This mod also ships 2 executable files (scripts/compare_box3_annual_2025.py, scripts/summarize_box3_provisional_2026.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

plugins/nl-tax-agent-skills/skills/nl-tax-box3/SKILL.md · 117 lines

How it starts

The opening of the file, as written. The whole thing — 117 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 notes.

Annual 2025 must cover fictitious return and werkelijk-rendement data collection for user review. Provisional 2026 must use only the provisional fictitious method and must never ask for werkelijk rendement.

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 calling skill 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.

Hard rules

  • Annual 2025: collect and compare fictitious return and werkelijk rendement when the user wants the actual-return comparison.
  • Ask only branch-applicable annual inputs. A savings-only case needs the 1 January balance for the fictitious method and actual 2025 interest for an actual-return comparison; it does not need a 31 December bank balance merely because the comparison was offered.
  • Provisional 2026: use only the fictitious method.
  • Never request werkelijk-rendement inputs in a provisional workflow.
  • In provisional 2026, accept a debt into schulden only after the official inclusion/exclusion screen. Do not use "all debts except the own-home mortgage" as a shortcut; unresolved debts remain manual-review rows outside accepted totals.
  • Compute only from values with a real source or an explicitly confirmed assumption.
  • The agent classifies each row from the reviewed facts and official rules. Python never infers a category from a description, name, or keyword.
  • Before arithmetic, represent every row with category, status, value, and provenance. Only status: "accepted" rows in banktegoeden, overige_bezittingen, or schulden, with finite non-negative values and non-empty provenance, enter trusted totals. Keep every other row in a rejected/manual-review table with a reason.
  • The bundled scripts require --partner-full-year-confirmed alongside --has_partner before they double the heffingsvrij vermogen and the schulden drempel; --has_partner on its own raises an error. They also reject negative or non-finite amounts. Do not present a doubled allowance until full-year partnership is confirmed.

Read the full file on GitHub · 117 lines

Files

What ships with it

6 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.

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. 12d ago First seen · 117 lines · 43 tokens per session scan A 6403a2e75bf6

Subscribe to this mod's changes

nl-tax-box3 is a skill published in the GitHub repository cyanxxy/nl-tax-agent-skills (10 stars, last pushed 17d ago), licensed Apache-2.0. It adds 43 tokens to every session and 1,548 once invoked, about $0.0002 per session on Opus 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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