Syntactic interoperability is table stakes.

Healthcare APIs built for semantic interoperability

Our APIs are built on FHIR, so they're modern and fast to integrate. The semantics are the hard part. We bring clinical and informatics expertise to get the meaning right, and to enrich your data where we can add real clinical value.

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APIs on the platform

open standards we build on

FHIR R4 validated

slots normalized

Why haau3

Two layers of interoperability

Modern FHIR APIs solve syntactic interoperability: data shaped to a shared standard that systems can exchange. But well-formed data can still be wrong or incomplete in meaning. That semantic layer is where we focus.

Syntactic · structureSemantic · meaning

FHIR resourceconformant

codeCodeableConcept

specimenReference

valueCodeableConcept

componentCodeableConcept

FHIR resourcemeaning added

codeBlood culture

specimenBlood

valueS. aureus

componentGram-positive

Syntactic

Data shaped to a shared standard so systems can exchange it. FHIR R4 conformance is the floor; from there we validate against the implementation guides each use case calls for, from US Core to SMART Scheduling Links to the Da Vinci profiles. You get data that is valid for how you actually use it.

Semantic

Correct structure does not mean correct meaning. We bring clinical and informatics expertise to validate and standardize your data, then enrich it where we safely can: reading an Observation's LOINC code to recognize a lab and stamp the right category, or de-duplicating a medication list across RxNorm and ATC. The clinical content behind every API is vetted.

One platform. Every healthcare API.

Start with provider scheduling today. Medications, provider directory, terminology, synthetic patients, and health-link sharing are on the way.

FreeAvailable

Scheduling API

A Slot Aggregator for SMART Scheduling Links. It brings provider availability from many publishers into one normalized API.

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Soon

MedList API

Structured, reconciled medication lists for patients. The data layer behind MedListIQ.

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FreeAvailable

Provider Directory API

Resolve an NPI to the practitioner behind it, and to where they practise. Backed by the CMS National Directory, served as FHIR.

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Available

Terminology API

A hosted FHIR terminology service. Look up codes, expand value sets, and validate codes against standard code systems, getting back the standard FHIR response.

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Soon

Synthetic Patients API

Generate realistic synthetic FHIR patients on demand. PHI-free test data for building, testing, and demos.

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Soon

Health Links API

Create SMART Health Links and Health Cards so patients can share their records with a tap. Part of the push to kill the clipboard.

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Soon

Decision Support API

Build EHR-agnostic clinical decision support with CDS Hooks, backed by guideline content as FHIR PlanDefinitions.

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Soon

Drug Interaction API

Screen a medication list for drug–drug and drug interaction risks through one API.

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Soon

Device Data API

Integrate wearable and remote-monitoring device data into your product through one normalized API.

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One platform. Every healthcare API.

Start with provider scheduling today. Medications, provider directory, terminology, synthetic patients, and health-link sharing are on the way.

Scheduling API
MedList API
Provider Directory API
Terminology API
Synthetic Patients API
Health Links API
Decision Support API
Drug Interaction API
Device Data API

01/09

Scheduling API

FreeAvailable

A Slot Aggregator for SMART Scheduling Links. It brings provider availability from many publishers into one normalized API.

FHIR R4SMART Scheduling LinksBulk FHIR

Learn moreGETapi.haau3.com/v1/scheduling/slots

Open standards for structure and meaning

Exchange

FHIR R4SMART Scheduling LinksSMART Health LinksSMART Health CardsUS CoreCMS National DirectoryKill the ClipboardFHIR R4SMART Scheduling LinksSMART Health LinksSMART Health CardsUS CoreCMS National DirectoryKill the Clipboard

Meaning

LOINCSNOMED CTICD-10RxNormCVXUCUMLOINCSNOMED CTICD-10RxNormCVXUCUM

Audit trail

Every change, on the record

Semantic work means changing data, so we record every change. Each enrichment or normalization writes a FHIR Provenance resource, giving you a complete audit trail of what we touched, when, and why.

Read the docs View pricing

provenance.json

{
  "resourceType": "Provenance",
  "target": [{ "reference": "Observation/blood-culture" }],
  "recorded": "2026-06-21T14:02:11Z",
  "activity": { "text": "Enrichment: added organism classification" },
  "agent": [{ "who": { "display": "haau3" } }],
  "entity": [
    { "role": "source", "what": { "display": "S. aureus" } }
  ]
}

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Create an organization and explore the Scheduling API today, free during the community preview.

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{ "resourceType": "Provenance", "target": [{ "reference": "Observation/blood-culture" }], "recorded": "2026-06-21T14:02:11Z", "activity": { "text": "Enrichment: added organism classification" }, "agent": [{ "who": { "display": "haau3" } }], "entity": [ { "role": "source", "what": { "display": "S. aureus" } } ] }