Core concepts
Concepts & quality tiers
Skills, facts, jurisdictions, verification, workflows — and the warranted accountant who makes the output something a user can rely on.
A handful of concepts run through everything in OpenAccountants. Understanding them makes the API and the MCP tools self-explanatory.
Skills
A skill is a markdown document that teaches an AI agent how to do one tax or accounting computation — a Malta VAT return, a US Schedule C, a UK capital-gains calculation. Skills are agent-agnostic: they work with any AI agent that reads markdown. There are roughly 1,100 published skills across 190+ jurisdictions, at country and US-state level.
Facts
Under each skill sits a set of facts — the individual, structured figures a skill is built from (a rate, a threshold, an allowance, a deadline), each cited to its source. Facts are the single source of truth: the prose you read is generated from the facts, not maintained alongside them. That's what keeps a corrected number from drifting between the data and the document.
Quality tiers
Every skill carries one of two tiers — and only two. The labels are deliberate, because they describe reliance risk.
| Tier | Label | What it means |
|---|---|---|
| Q1 | Accountant-verified | A named, licensed accountant (CPA / EA-equivalent) reviewed it against the source and signed it. |
| Q2 | Source-cited draft | Drafted from authoritative sources and cited, but not yet reviewed by a credentialed accountant. |
A Q2 skill is honest about what it is: cited, but unreviewed. It is not "verified," "certified," or "guaranteed." Tier labels travel with the data wherever you pull it, so you always know what carries an accountant's sign-off.
Jurisdictions
A jurisdiction is a country or a US state (codes like MT, GB, US, US-CA, CA-ON). Coverage and the named lead verifier per jurisdiction are available via the list_jurisdictions MCP tool and the bundle endpoint.
Verification
Verification is the act of a named licensed accountant signing off on skills — surfaced through list_verifiers and the tier labels. Verification is what moves a skill from Q2 to Q1.
Workflows
A workflow is a guided, multi-step procedure authored by verified accountants that wires several skills together in order (for example, "prepare a Malta VAT return"). Discover them with list_workflows, load one with get_workflow, and see its structure with inspect_workflow.
The warranted accountant
When a number is going to be relied upon — filed, or acted on with consequences — a warranted accountant reviews it and signs with professional liability. A named, licensed professional in the user's jurisdiction.
This is the part that matters most. "An app told me" is not a defence to a tax authority; a warranted accountant is. The rules are open and cited so anyone can build on them — but the credentialed human accountability is what turns a confident answer into something a user can rely on. That's why the accountant directory and the request_accountant_review tool exist.