XBRL
An open standard for tagging business and financial reporting data against defined taxonomies, mandated for filings by numerous regulators including the SEC.
Why it matters for autonomous finance
The most durable lesson on this list, and it is a cautionary one. XBRL is what happens when a machine-readable standard is mandated before the semantics are settled: two decades in, filers still use custom extension elements heavily, which means comparability — the entire point — remains partial. Anyone designing a conformance regime for agent governance should study XBRL's extension problem before writing a single schema, because the same failure is available and nobody is watching for it.
What it does not cover
Machine-readable is not machine-comparable. A tagged document with bespoke extensions is structured and still not interoperable. Read XBRL as evidence that format standardisation without vocabulary discipline produces the appearance of interoperability rather than the substance.
Reporting-scoped; no runtime, authority, or oversight semantics. Every entry in this register carries this section. A standard read past its scope is worse than no standard, because it produces confidence without coverage.