Unified APIs from Merge, Kombo, Finch, and Papaya have a structural coverage gap. They only supply APIs for the most common payroll engines, and only for core data. Country-specific local providers, the structural depth of payroll result tables, and the specialized fields required for statutory reporting are not exposed. The interface is partial, not full. Beyond coverage, canonical schemas flatten country-specific compensation components into generic fields, breaking bidirectional flow. The pipe works. The fluid is contaminated and the long tail is unsupported.
