All writes require contract negotiation with eClinicalWorks. Cobalt has existing write access.

No native webhooks. Cobalt provides real-time data feeds via HL7v2 integration.

Per-practice activation and build version management is complex. Cobalt handles multi-practice provisioning.

eClinicalWorks offers solid FHIR R4 read coverage and reasonable write capabilities, but every write operation requires a separate contract. There are no webhooks — event-driven patterns require HL7v2 middleware.

eClinicalWorks

eCW FHIR Developer Portal

eCW FHIR Documentation

healow Developer Portal

healow FHIR Documentation

Interoperability Overview

ONC Certification Page

EHI Export Documentation

Zus Health — eCW Integration

Iguana — eCW Integration Guide

FHIR R4 + HL7v2. Read access is self-service; all writes are contract-gated. No webhooks.

Notes write requires SMART app embedding and scope approval. Cobalt provides a unified write interface.

Push-based event subscriptions are alpha-only and scopes aren't self-service. Cobalt provides production-ready eventing.

Quarterly breaking changes require continuous maintenance. Cobalt absorbs API version management.

athenahealth has the broadest API surface of the EHRs reviewed, with 800+ proprietary endpoints covering clinical, scheduling, and billing workflows. However, clinical notes write requires embedded SMART apps, and the push-based event system is still in alpha.

athenahealth

Main API Docs

Developer Console

All APIs Reference

FHIR APIs

athenaOne Core IG v5.8.0

Onboarding Guide

Authorization Overview

Changed Data Subscriptions

FHIR Event Subscriptions

ONC Certification

Marketplace Partners

Developer Portal Overview

800+ proprietary REST endpoints + FHIR R4. Broadest write coverage. Self-service sandbox.

No write API exists for clinical data. Cobalt provides write access through alternative integration pathways.

No scheduling API exists. Cobalt enables appointment workflows for Practice Fusion.

No webhooks or event-driven integration. Cobalt provides real-time data access.

Unclear onboarding path with no developer portal. Cobalt has an established integration with Practice Fusion.

Practice Fusion is effectively read-only for third-party integrators. There is no write API for clinical data, no scheduling API, no webhooks, and the developer onboarding path is unclear.

Practice Fusion

FHIR API Specifications

PDS API Developer Guide

Labs Documentation

ONC Certified EHR

PDS Registration Portal

Veradigm FHIR Endpoint Directory

Read-only FHIR R4. No write API, no scheduling, no webhooks. High integration barrier.

No webhooks available. Cobalt provides real-time event-driven data from ModMed.

Dual API track with different auth methods is complex. Cobalt provides a single unified interface.

Per-practice credential management creates operational overhead. Cobalt handles credential lifecycle.

ModMed provides strong write access through its proprietary FHIR API after a partner onboarding process. The dual-track API architecture (proprietary vs. certified) means maintaining two integration paths with different auth methods.

ModMed

API Portal

Proprietary API Documentation (PDF)

Certified FHIR API Documentation (PDF)

ONC Certification Press Release

Become a Partner

Certified API Vendor Registration

FHIR Endpoint Directory

synapSYS Marketplace

Dual-track FHIR R4 APIs with strong write access. Self-service writes after partner onboarding.

EHR API Explorer

eClinicalWorks

athenahealth

Practice Fusion

ModMed

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