io.github.Invaro/opentax is an MCP server with 15 tools an agent can call, among them calculate_business_tax, calculate_fiduciary_tax, calculate_tax. It answers at https://opentax.invaro.ai/mcp over streamable HTTP, and it listed its tools to an anonymous client, so no sign-in was needed for that. Our probes reached it 6 of 6 times since 11 September 2026; the last check, on 20 October 2026, succeeded.
Verifiable US tax oracle for AI agents: cited, machine-checkable federal and state tax computation
Description as the publisher wrote it.
| Tool | What it does |
|---|---|
calculate_business_tax | Compute US federal BUSINESS-ENTITY tax from the same cited corpus: check-the-box entity classification, Form 1120 corporate income tax (§ 179/168(k)/174A/163(j)/DRD/NOL, § 250, GBC/FTC/BEAT), S-corp entity taxes, corporate estimates, the § |
calculate_fiduciary_tax | Compute US federal income tax for an ESTATE or TRUST (Form 1041): the § 1(e) compressed brackets and § 642(b) exemption. Input is taxable income before the exemption, after the §§ 651/661 distribution deduction. Retained capital gains refus Inputs: fiduciaryType, fiduciaryIncomeBeforeExemption, fiduciaryLongTermGains, target, asOf, includeProof |
calculate_tax | Compute US federal INDIVIDUAL income tax (or balance due if withholding is given) from a content-addressed corpus of cited rules. NEVER estimate tax yourself — call this, and report ONLY numbers returned by oracle calls made with the real f |
compare_filing_statuses | Compute the answer under every filing status for the same facts — e.g. to answer 'should we file jointly or separately?'. Statuses that need more facts report their error instead of guessing. Inputs: facts |
compute_return | Compute the COMPLETE Form 1040 bottom-line set in one call — the 17 lines that determine the return (1a, 9, 10, 11, 12e, 15, 16, 17 AMT, 19, 22, 23, 24, 25d, 27a, 28, 32, 33, 34/37), each whole-dollar rounded by the engine. Takes the SAME i |
compute_state_return | Compose a STATE return's printed-form line set deterministically (2025 IL-1040 / VA 760 / CA 540 / NY IT-201 / PA-40 / NJ-1040 / OH IT 1040 / NC D-400 / GA 500 / MD 502 / MO-1040 / WI Form 1 / MN M1 / SC1040 / AL Form 40 / OR-40 / OK Form 5 |
determine_dependent | Determine whether ONE candidate person is the taxpayer's § 152 dependent — qualifying child or qualifying relative, including multiple-support agreements and the divorced-parents release — as a proof-backed yes/no with citations. Feed the r Inputs: depRelationshipChild, depAge, depIsFullTimeStudent, depPermanentlyDisabled, depYoungerThanTaxpayer, depLivedWithTaxpayerOverHalfYear |
explain_rule | Get a tax rule's statutory citation, verbatim excerpt, validity window, parameters, and dependencies. Use to quote the actual law behind an answer. Inputs: ruleId |
find_tax_cliffs | Find exact dollar amounts where one more cent of an input costs MORE than a cent of tax (marginal rate over 100%) — e.g. the EITC investment-income kill switch, CTC phase-out steps. Every probe is a real evaluation. Inputs: facts, vary, fromDollars, toDollars, stepDollars |
is_tipped_occupation | Determine whether a job is on the Treasury Tipped Occupation list (Treas. Reg. § 1.224-1, final Apr 2026) for the § 224 'no tax on tips' deduction. Fuzzy-matches the job name; returns the official listing (name, TTC code, category) or a def Inputs: job |
list_input_facts | Discover every input the tax corpus understands: id, type, whether required, and its documented default. Call this if unsure what information to collect from the user. |
lookup_tax_parameter | Look up the current-law dollar amounts behind a question ('standard deduction', 'CTC phase-out threshold', 'tips deduction cap') with their statutory citations and validity windows. Use this to fact-check ANY tax number before stating it — Inputs: query, asOf |
search_tax_rules | Full-text search over the encoded tax-law corpus ('kiddie tax', 'NIIT threshold', 'california renters credit'). Returns matching rules: id, title, statutory citation, effective window, and a verbatim excerpt of the law text. A hit means the Inputs: query, asOf, limit |
verify_fact | Fact-check a claimed dollar amount about tax law ('the 2026 MFJ standard deduction is $32,200', 'CTC is $2,000 per child') against the corpus. Returns verified / refuted (with the correct value and citation) / unknown. Never states a verdic Inputs: query, claimedAmount, filingStatus, asOf |
verify_tax_claim | Verify a claimed tax amount (yours, a user's, or another tool's) against the law. Returns verdict 'verified' or 'refuted' with the correct value. Use this as a self-check before presenting any tax number. Put asOf (and target, if any) INSID Inputs: facts, claimedAmount, toleranceDollars |
Every block below points at https://opentax.invaro.ai/mcp. Pick your client and copy.
claude mcp add --transport http io-github-invaro-opentax https://opentax.invaro.ai/mcp
{
"mcpServers": {
"io-github-invaro-opentax": {
"command": "npx",
"args": ["-y", "mcp-remote", "https://opentax.invaro.ai/mcp"]
}
}
}{
"mcpServers": {
"io-github-invaro-opentax": {
"url": "https://opentax.invaro.ai/mcp"
}
}
}{
"servers": {
"io-github-invaro-opentax": {
"type": "http",
"url": "https://opentax.invaro.ai/mcp"
}
}
}{
"context_servers": {
"io-github-invaro-opentax": {
"url": "https://opentax.invaro.ai/mcp"
}
}
}{
"mcpServers": {
"io-github-invaro-opentax": {
"serverUrl": "https://opentax.invaro.ai/mcp"
}
}
}{
"mcpServers": {
"io-github-invaro-opentax": {
"url": "https://opentax.invaro.ai/mcp"
}
}
}name: io.github.Invaro/opentax
version: 0.0.1
schema: v1
mcpServers:
- name: io.github.Invaro/opentax
type: streamable-http
url: https://opentax.invaro.ai/mcp{
"mcpServers": {
"io-github-invaro-opentax": {
"httpUrl": "https://opentax.invaro.ai/mcp"
}
}
}{
"mcpServers": {
"io-github-invaro-opentax": {
"type": "http",
"url": "https://opentax.invaro.ai/mcp"
}
}
}{
"mcpServers": {
"io-github-invaro-opentax": {
"url": "https://opentax.invaro.ai/mcp"
}
}
}goose://extension?url=https%3A%2F%2Fopentax.invaro.ai%2Fmcp&type=streamable_http&id=io-github-invaro-opentax&name=io.github.Invaro/opentax
It answered our last check on 20 October 2026 in 200 ms. Over 6 checks since 11 September 2026 it answered 6. Status here comes from Neuronto's own probes, not from the publisher.
15, as returned by the server's own tools/list on 12 September 2026: calculate_business_tax, calculate_fiduciary_tax, calculate_tax, compare_filing_statuses, compute_return, compute_state_return, determine_dependent, explain_rule, and 7 more.
It answered our last check on 20 October 2026 in 200 ms. Over 6 checks since 11 September 2026 it answered 6.
Put the server under mcpServers in ~/.cursor/mcp.json with the URL https://opentax.invaro.ai/mcp. The exact JSON is above, with the same setup for Claude Code, Claude Desktop, VS Code, Windsurf, Zed, Gemini CLI and the rest.
It listed its tools to an anonymous client, so reading the tool list needs no key. Individual tools can still ask for credentials in their own inputs.
Publisher: io.github.invaro. Endpoint host: opentax.invaro.ai. ARD identifier: urn:air:io.github.invaro:mcp:opentax.
First indexed 10 September 2026. The tools are exactly what the server returned; nothing on this page
is inferred from its name. Ranking in Neuronto search is never for sale.