Tax Numbers in Pi
US tax figures, IRS-sourced. The MCP server is https://tax.openkrill.app/mcp. No key. The steps below are only for Pi. A call to get_tax_parameters was checked against that server on 2026-10-01.
What this server answers
Get the US federal tax numbers right, with the IRS document each one comes from.
Ask "what are the 2026 tax brackets for a married couple?", "what is the standard deduction for head of household?", "what was the IRS mileage rate on 15 March?", "when is the next estimated tax payment due?" or "roughly how much federal tax on 90,000 dollars of wages and 30,000 dollars of freelance income?".
Tax Numbers holds the federal income tax figures for tax years 2025 and 2026: brackets, standard deduction, long-term capital gains thresholds, the Social Security wage base and self-employment tax, 401(k) and IRA limits, the standard mileage rates, and the filing and estimated-payment deadlines. Every figure comes with the Revenue Procedure, notice or IRS page it was read from, and every answer says when the table was last verified. A year is added only after all of its figures have been checked.
It can also work out a simple federal estimate: standard deduction only, with self-employment tax, long-term capital gains and the Additional Medicare Tax. Every estimate lists its assumptions and what it leaves out (credits, state tax, alternative minimum tax, itemized deductions and more), and says it is an estimate and not tax advice.
It does not fill in or file returns, give advice on what to do, or cover state taxes. Your figures are used for the one calculation and are not stored; the only lasting record is a daily count of calls per tool.
What it can do
- Looks up federal tax brackets, standard deduction and capital gains thresholds with IRS citations
- Gives the Social Security wage base and self-employment tax rules
- Gives 401(k) and IRA contribution limits
- Finds the IRS standard mileage rate for any date
- Lists filing and estimated-payment deadlines for a tax year
- Estimates federal tax with stated assumptions and exclusions
Tools
get_tax_parameters, Look up US federal tax figures. Use this when the user asks for a published US federal tax figure, for example "what are the 2026 tax brackets for married filing jointly", "standard deduction for head of household in 2025", "long-term capital gains thresholds", "Social Security wage base", "401(k) contribution limit". Pass the tax year (2025 and 2026), the topic (brackets, standard_deduction, mileage, retirement_limits, capital_gains, self_employment or all) and optionally the filing status (single, mfj, mfs, hoh). Returns rows with the figure and the IRS document and section it was read from, the year's status (current, or amended when a later law or notice changed a figure, with amended_by), and when the table was last verified. It does not give advice and does not cover state taxes.get_mileage_rate, Look up the IRS mileage rate. Use this when the user asks for the IRS standard mileage rate on a day, for example "what was the business mileage rate on 15 March 2026", "how much per mile can I deduct for charity driving", "medical mileage rate in 2025". Pass the date (YYYY-MM-DD); the rate in force that day is returned in cents per mile for business, medical and charity use, with the period it covers, the IRS notice that announced it and when it was last verified. Rates are available from 1 January 2022. It does not add up trips or compute a deduction.tax_deadlines, List US federal tax deadlines. Use this when the user asks when a US federal individual tax date falls, for example "when is the 2025 return due", "when is the extension deadline", "when is the next estimated tax payment due". Pass the tax year (the year the income was earned) and optionally as_of (today, YYYY-MM-DD) to get the next deadline. Returns the four estimated payment dates, the filing date and the extended filing date, each with whether the IRS publishes it or it follows the standing rule, and its source. Weekend and holiday moves are already applied. It does not cover state deadlines or disaster-relief postponements.estimate_federal_tax, Estimate US federal income tax. Use this when the user wants a rough US federal income tax figure, for example "how much federal tax on 90,000 dollars of wages", "estimate my tax with 40,000 dollars of freelance income", "what is my marginal rate". Pass the tax year, filing_status (single, mfj, mfs, hoh) and wages in dollars, and optionally self_employment_income, other_ordinary_income, long_term_capital_gains and adjustments. It uses the standard deduction and adds self-employment tax (with the Social Security wage base and the half-deduction), the Additional Medicare Tax and long-term capital gains rates. Returns taxable income, ordinary tax, capital gains tax, self-employment tax, total, marginal and effective rate, the assumptions made and a not_included list (credits, state tax, alternative minimum tax, itemized deductions and more). It is an estimate, not tax advice, and it is not a return.
Add Tax Numbers in Pi
Pi does not speak MCP on its own. The pi-mcp-adapter extension (these steps match version 2.34.0) loads remote servers and keeps their schemas out of the prompt until you ask. Install it once, then restart Pi:
pi install npm:pi-mcp-adapterAdd the server to a shared MCP file. Use .mcp.json in the project if only that project needs Tax Numbers, or ~/.config/mcp/mcp.json if you want it in every project. Pi also reads ~/.agents/mcp.json. A Pi-only override lives in ~/.pi/agent/mcp.json or .pi/mcp.json and wins over the shared file.
{
"mcpServers": {
"tax": {
"url": "https://tax.openkrill.app/mcp"
}
}
}The url is enough. Do not set command: that field is for a local process. No API key header. After restart, run /mcp and confirm the server is listed. The first call connects lazily. Ask: What is the 2026 standard deduction for a single filer? The adapter should offer get_tax_parameters, get_mileage_rate, tax_deadlines, estimate_federal_tax.
Leave directTools off unless you want those schemas in every turn. With a handful of tools the cost is small. The default proxy is the better fit: search for the tool, then call it. /mcp disable tax writes a project override in .pi/mcp.json without editing the shared file. Run /reload after that change.
Pi will not find this server by scanning Cursor or Claude config unless you run /mcp setup and import it. Putting the url in .mcp.json is the direct path and the one this page tests against. The server is the same public endpoint the other clients use, with the same limits and the same privacy rules.
A call checked on 2026-10-01
The 2026 single-filer standard deduction is a published IRS figure in the plugin's table. It is not tax advice. The request below was posted to https://tax.openkrill.app/mcp as tools/call. HTTP 200. Source: the Tax Numbers server, read 2026-10-01.
{
"method": "tools/call",
"params": {
"name": "get_tax_parameters",
"arguments": {
"year": 2026,
"topic": "standard_deduction",
"filing_status": "single"
}
}
}- status. current
- year. 2026
- rows. 2 returned
- source document. Rev. Proc. 2025-32 (2026 inflation adjustments)
- source date. 2025-10-09
Repeat the call yourself if you need a newer reading. Cached answers expire. A rate limit is not a result: wait and try again. Nothing in the call is a ranking, a filing, or advice.