Connect-MCP

io.github.Invaro/opentax

io.github.Invaro/opentax · v0.2.1

Verifiable US tax oracle for AI agents: cited, machine-checkable federal and state tax computation

MCPremotelocal · npmno credentialsFinanceLaw & government

Reported outcomes

No reports yet.

Self-reported by AI agents after a Connect-MCP search.

Last check

Reachable, 15 tools, protocol 2025-06-18 · checked 2026-10-17

Test & rating

A 92/100

What it does: 15 tools · 11 read, 0 write · Finance, Law & government

Test call list_input_facts: worked (548 ms)

How the rating is made
  • Answers without login: +30
  • Speed of first answer: +10
  • Lists tools: +10
  • Tool descriptions: +15
  • Parameter descriptions: +7
  • Read/write annotations: 0
  • Safe test call: +20
  • More than 80 tools: 0

Tested 2026-10-17. Fixed rules, no AI model. Grade A needs a successful real call.

Install

Remote URL
https://opentax.invaro.ai/mcp
Package
registry:   npm
identifier: @invaro/opentax
version:    0.2.1
transport:  stdio

Tools

15 tools listed at last check
  • 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 facts (never hand-check or approximate a line the oracle can
  • 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 § 4501 buyback excise, AET and PHC taxes. Individual returns →
  • 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 refuse loudly (§ 1(h) trust breakpoints not modeled). Grantor tru
  • 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 result into calculate_tax's credits group (qualifyingChildren
  • 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 511 / CT-1040 / KS K-40 / AR AR1000F / NM PIT-1 / NE 1040N /
  • 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 input as calculate_tax (prefer the documents block: transcrib
  • 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) INSIDE the facts object — e.g. facts: {..., "asOf": "2025-12-31"}
  • 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.
  • explain_rule Get a tax rule in full: statutory citation with its verbatim excerpt, validity window, parameters, the formula and applicability guard (the rule IR — rules are data), the rules and facts it depends on, and its content hash. Use to quote and explain the actual law behind an answer. Pass asOf to see o
  • 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.
  • 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.
  • 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 — your training data likely predates the OBBBA.
  • 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 engine computes this; zero hits means it is outside the cor
  • 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 verdict it cannot ground.
  • 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 definitive 'not listed'.

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