Endpoint URL validity + machine-readable share
Of the 1.36M Endpoint resources in the NDH bulk export, only 8.4% are FHIR REST URLs an integrator can GET. The other 91.6% are Direct Trust HISP messaging addresses, which solve a different problem entirely. The right denominator for any "find FHIR endpoint by NPI" feature is the FHIR REST subset — not the full Endpoint resource count.
Headline
Of 1,360,585 Endpoint resources in the 2026-05-08 NDH bulk export, only 114,071 (8.4%) are machine-readable FHIR REST URLs an integrator can GET. The remaining 1,246,514 (91.6%) are Direct Trust HISP addresses (clinical messaging, not a queryable API), and 0 use other connection types. The 8.4% machine-readable share is the right denominator for any "find the FHIR endpoint for this provider" feature built on top of NDH.
114.1K / 1.4M = 8.38%
unit: count
What this means
Startups + integrators
When sizing a "find this provider's FHIR endpoint" product, the right population is 114K hl7-fhir-rest endpoints — not 1.36M total. Direct Trust HISP addresses (provider@hisp.example.com) are clinical-messaging routes, not API URLs; treating them as substitutable will fail at integration time.
Payer ops teams
CMS-9115-F adequacy reads against the FHIR REST subset only. The 8.4% machine-readable share is your effective denominator for compliance reporting, not the headline 1.36M total Endpoint count.
CMS publishing the data
Two values share one Endpoint resource shape today. Splitting the published count by `connectionType` (or publishing a top-level "machine-readable endpoints" counter) would make the resource census far less misleading at a glance.
Researchers
Reports that compare "endpoint counts across releases" should split by connection type. The 73% drop in raw Endpoint count between April 2026-04-09 and May 2026-05-08 is dominated by Direct Trust dedup; the FHIR REST count is much steadier.
Null hypothesis
100% of NDH `Endpoint.address` values are well-formed for their declared `connectionType`. There is no surprising shape mismatch between connection-type-by-count and machine-readable share.
Denominator
All `Endpoint` resources in the pinned NDH bulk export.
Data source
BigQuery scan of `cms_npd.endpoint`, partitioned by `_connection_type` and validated against `_address` regex by type.
Notes
NDH ships two distinct connectionType.code values that share an Endpoint shape: hl7-fhir-rest (FHIR REST API URLs) and direct-project (Direct Trust HISP messaging addresses, of the form provider@hisp.example.com). Both are valuable but solve different problems. Of the 114,071 hl7-fhir-rest endpoints, 100% have a valid https:// URL — there is no http:// or malformed URL noise in this slice. 98,819 are flagged status=active. Crawler liveness (/findings/endpoint-liveness, H1-H5) probes the active subset. For consumers wiring 'find FHIR endpoint by NPI' — the right denominator is the 114,071 hl7-fhir-rest endpoints, NOT the 1,360,585 total resource count. This was a non-obvious cliff in the data quality dashboard until H28 surfaced it.