The compliant-output layer for comp importers.

Published rules, not a black box.

Most QC tools score your file with a proprietary rubric and hand back a pass/fail you can't trace. Plumb loads the Appendix H-1 workbook — v1.5, dated 2026-08-13 — directly from the GSE publication and reports the exact number of rules evaluated. Every finding cites the rule ID (UAD####), the severity (Fatal / Warning / Informational), and the workbook text. If a finding fires, you can look it up in the published rules and see why. If you disagree, you disagree with the GSEs' own rule, not Plumb's opinion.

The workflow split.

Comp importers are good at data-IN — pulling comps, normalizing addresses, assembling the grid. They are not built to emit UAD 3.6 MISMO XML or run the GSE compliance ruleset. Plumb is the UAD-XML-OUT half: a structured-ingest API that takes your JSON, maps it onto the MISMO model, validates against the XSD, and runs the published compliance engine. You keep your importer; Plumb rides alongside as the output layer.

The split is honest about scope. Plumb's conversational capture flow is SFR-first today. The structured ingest path covers more ground — the 13 fixture archetypes prove SFR, condo, 2–4 unit (with per-unit rent schedule and GRM income approach), and new-construction-subject-to-completion end-to-end. If your importer covers a shape the chat doesn't yet capture, the ingest path is the one to use.

What Plumb returns.

• UAD 3.6 MISMO XML — XSD-validated against GSE_UAD_3.6.0_v1.3 for the UCDP delivery workflow.
• Appendix H-1 compliance report — each finding from the rules evaluated, cited by rule ID with the workbook text and the exact evaluated count. The loaded corpus contains 508 Fatal rules, 628 total.
• PDF — the redesigned URAR layout (Appendix C-1), rendered from the same model that produced the XML.

Honesty rules.

• Absent stays absent. A field your importer didn't supply is omitted from the XML — never silently defaulted. Missing R-required fields surface as compliance findings, not invented values.
• No fabricated appraisal judgments. Plumb doesn't invent condition ratings, quality ratings, or reconciliation narratives. You supply the facts; Plumb structures and validates them.
• The rules come from the published workbook. No proprietary score is substituted for them. Every finding is traceable to a GSE-published rule ID, and the report states how many rules were evaluated.

The ingest spec.

The full field-level contract is in Plumb ingest spec — one JSON object with three required blocks (subject, comparables, valuation) plus optional blocks for site, structure, amenities, defects, and 2–4 unit / income-approach data. Your payload validates against schemas/plumb_ingest_v1.schema.json; docs/plumb_ingest_v1.md carries the field-to-UAD-UID mapping.

For TrueTracts, DataMaster, and equivalent importers.

The ingest format is importer-agnostic. If your export can produce the subject + comp grid + valuation JSON described in the spec, Plumb can produce XSD-validated UAD 3.6 XML from it. Integrations welcome — email hello@plumbvaluation.com.