Firely is an Amsterdam-based health IT company and one of the original co-developers of the HL7 FHIR (Fast Healthcare Interoperability Resources) specification. Co-founded by Ewout Kramer and Martijn Harthoorn (both long-time HL7 FHIR core team members), Firely builds the canonical FHIR toolchain used by payers, providers, health authorities, and digital health vendors worldwide. The Firely platform is anchored by Firely Server (formerly Vonk) — a certified production-grade FHIR server with native support for MongoDB and SQL Server, deployable on Windows, Linux, macOS, Docker, and Kubernetes across on-premise, Azure, AWS, and Google Cloud. Firely Server is G10, ONC, and ISiK certified and supports SMART on FHIR, Bulk Data, CDS Hooks, Subscriptions, Terminology Services, and FHIR Mapping. The product family also includes Simplifier.net (the global FHIR profile registry and package server hosting ~9,000 projects, 40,000+ profiles, and 1,600+ implementation guides), Forge (FHIR profile editor), Firely Terminal (command-line FHIR tool with FQL/FSH/FHIRPath support), the open-source Firely .NET SDK (the de-facto reference C# FHIR library), the firely-cql-sdk for Clinical Quality Language, the Firely Validator API, FHIR Facade, Firely Server Ingest, and Firely Auth. Customers include UCSF, Humana, Roche, NHS, Opala, and the World Health Organization. Firely does not operate a hosted multi-tenant FHIR-as-a-service offering with a public REST endpoint; customers run Firely Server in their own environments. The public developer surface is therefore the Firely software products (Firely Server, .NET SDK, Terminal), the Simplifier.net package and registry APIs, and the open HL7 FHIR REST API contract that every Firely Server instance implements.
Firely publishes 3 API contracts indexed on the APIs.io network, including Catalog API, Simplifier.net FHIR Package API, and 1 more. Tagged areas include FHIR, HL7, Healthcare, Health IT, and Interoperability.
The Firely catalog on APIs.io includes 1 Spectral governance ruleset.
Firely’s developer surface includes developer portal, documentation, tooling, code examples, pricing, signup flow, training material, and 48 more developer resources.
Regulatory Posture applies to this provider. Its tags matched the
Health regime, so
Regulatory Posture carries 15 points of the composite.
If this regime is wrong for your business, say so on your
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applicability map is public and we will correct it.
Create-or-Update Ergonomics does not apply to this provider. The published contracts declare
no write operations, and a read-only API cannot create-or-update. The facet is excluded from this provider's
denominator entirely — not scored zero. A reference or data API is not deficient for being unable to
upsert.
The six quality facets above are damped to 85 points between them,
because the conditional facet above carries the other
15. That is why each facet's contribution is shown against a damped
maximum: raising a quality facet moves the composite by 85% of its nominal
weight, not 100%. The full arithmetic is at apis.io/rating/.
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Agent readiness — checks not met, largest first (exact, from this profile):
MCP Server+12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship Ask about this →
Machine-Readable Auth+10 pts — a served openid-configuration/oauth-authorization-server carrying `issuer` (served), else the securitySchemes class in the provider OpenAPIs — bound (mutualTLS, DPoP, Signature) > negotiable (oauth2 authorizationCode/clientCredentials, openIdConnect) > bearer (http bearer, apiKey) Ask about this →
Stable Error Semantics+8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes Ask about this →
Rate-Limit Signaling+7 pts — OpenAPI responses document X-RateLimit-* / RateLimit headers (verified), else a rate_limits artifact or RateLimits link (documented) Ask about this →
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The Kin Score Market layer reads a provider inside its market:
its position, and how deep its integrations go. Depth is only comparable within a position. Provisional and unweighted:
not part of the Kin Score or agent readiness.
Registered MCP server and declares compatibility are report only — not weighted.
Undeclared means we found nothing we can read, so there is no number: we never infer integrations.
Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.
Every Firely Server (formerly Vonk) instance exposes the standard HL7 FHIR REST API contract — type-level and instance-level CRUD, search, history, batch/transaction, capability...
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