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 openaccountant/skills --skill tax-penalty-calcgit clone --depth 1 https://github.com/openaccountant/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/openaccountant/skills/tax-penalty-calc)<a href="https://agentmods.dev/skills/openaccountant/skills/tax-penalty-calc"><img src="https://agentmods.dev/badge/skills/openaccountant/skills/tax-penalty-calc/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/openaccountant/skills/tax-penalty-calc"><img src="https://agentmods.dev/badge/skills/openaccountant/skills/tax-penalty-calc.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 | $0.00018 | $0.00929 |
| Opus 5 | $0.00009 | $0.00464 |
| Sonnet 5 | $0.00004 | $0.00186 |
| Haiku 4.5 | $0.00002 | $0.00093 |
Grade A, and why
tax-penalty-calc 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 13d 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 — 80 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Tax Underpayment Penalty Calculator
Overview
Estimates the IRS underpayment penalty (Form 2210) for taxpayers who did not pay enough estimated tax during the year. The penalty is essentially interest charged on the underpaid amount for each quarter, calculated from the quarterly due date to the payment date or April 15 filing deadline.
Wilson Tools Used
transaction_search— Find estimated tax payments made to the IRS, EFTPS, or state tax authorities with dates and amountsspending_summary— Summarize total tax payments for the yearexport_transactions— Export payment history for Form 2210 preparation
Workflow
- Determine the total tax liability for the year (from your completed return or estimate).
- Calculate the required annual payment (lesser of 90% of current year tax or 100%/110% of prior year tax).
- Divide the required annual payment by 4 to get the per-quarter minimum.
- Use
transaction_searchto find all estimated tax payments, noting the date and amount of each. - For each quarter, compare what was paid by the due date against the required amount.
- For any quarter with a shortfall, calculate the penalty:
Penalty Calculation
penalty_per_quarter = underpayment_amount x (annual_rate / 365) x days_late
- The IRS penalty rate is set quarterly based on the federal short-term rate + 3 percentage points.
- As of early 2025, the rate is approximately 8% annually (verify at irs.gov/newsroom for current quarter).
- Days late = number of days from the quarterly due date to the earlier of: the payment date or April 15.
Quarterly Due Dates and Penalty Periods
| Quarter | Due Date | Penalty Runs Until |
|---|---|---|
| Q1 | April 15 | Payment date or April 15 of following year |
| Q2 | June 15 | Payment date or April 15 of following year |
| Q3 | September 15 | Payment date or April 15 of following year |
| Q4 | January 15 | Payment date or April 15 |
Example
- Required quarterly payment: $5,000
- Q2 payment made: $3,000 (shortfall of $2,000)
- Days from June 15 to April 15 = 304 days
- Penalty: $2,000 x (0.08 / 365) x 304 = $133.15
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.
- 13d ago First seen · 80 lines · 18 tokens per session scan A ef08617ea578
tax-penalty-calc is a skill published in the GitHub repository openaccountant/skills (67 stars, last pushed 5mo ago), licensed MIT. It adds 18 tokens to every session and 929 once invoked, about $0.0001 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 2026-08-30.
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