Metadata / CapabilityStatement

Overview

Returns a FHIR CapabilityStatement describing what operations and resources OMOPHub exposes at a given FHIR version endpoint. This is the first endpoint every conformant FHIR client hits - HAPI FHIR, Firely, Postman collections, and the inspectors built into most FHIR tooling all probe GET /metadata before making any other call.

Request

curl "https://fhir.omophub.com/fhir/r4/metadata" \
  -H "Authorization: Bearer YOUR_API_KEY"

Version variants

Path	FHIR version
`GET /fhir/metadata`	defaults to R4
`GET /fhir/r4/metadata`	R4 (4.0.1)
`GET /fhir/r4b/metadata`	R4B (4.3.0)
`GET /fhir/r5/metadata`	R5 (5.0.0)
`GET /fhir/r6/metadata`	R6 (6.0.0)

The response shape is version-adapted - field names follow the conventions of the requested FHIR version.

Response

{
  "resourceType": "CapabilityStatement",
  "status": "active",
  "kind": "instance",
  "fhirVersion": "4.0.1",
  "format": ["application/fhir+json", "application/fhir+xml"],
  "date": "2026-04-13",
  "publisher": "OMOPHub",
  "software": {
    "name": "OMOPHub FHIR Terminology Service",
    "version": "1.0.0"
  },
  "implementation": {
    "description": "OMOPHub FHIR Terminology Service - OMOP Standardized Vocabularies",
    "url": "https://fhir.omophub.com/fhir/r4"
  },
  "rest": [
    {
      "mode": "server",
      "resource": [
        {
          "type": "CodeSystem",
          "interaction": [
            { "code": "read" },
            { "code": "search-type" }
          ],
          "operation": [
            { "name": "lookup",        "definition": "http://hl7.org/fhir/OperationDefinition/CodeSystem-lookup" },
            { "name": "validate-code", "definition": "http://hl7.org/fhir/OperationDefinition/CodeSystem-validate-code" },
            { "name": "subsumes",      "definition": "http://hl7.org/fhir/OperationDefinition/CodeSystem-subsumes" },
            { "name": "find-matches",  "definition": "http://hl7.org/fhir/OperationDefinition/CodeSystem-find-matches" }
          ]
        },
        {
          "type": "ValueSet",
          "interaction": [
            { "code": "search-type" }
          ],
          "operation": [
            { "name": "expand",        "definition": "http://hl7.org/fhir/OperationDefinition/ValueSet-expand" },
            { "name": "validate-code", "definition": "http://hl7.org/fhir/OperationDefinition/ValueSet-validate-code" }
          ]
        },
        {
          "type": "ConceptMap",
          "operation": [
            { "name": "translate", "definition": "http://hl7.org/fhir/OperationDefinition/ConceptMap-translate" },
            { "name": "closure",   "definition": "http://hl7.org/fhir/OperationDefinition/ConceptMap-closure" }
          ]
        }
      ]
    }
  ]
}

The advertised format array includes application/fhir+xml because the server accepts XML requests via content negotiation. Most operations return clean XML; the three Bundle-shaped endpoints (CodeSystem search, ValueSet search, batch) are best-effort in XML and should be called with JSON in practice. See the XML support matrix in the overview for the per-endpoint breakdown.

Response headers

Every response from the FHIR Terminology Service - /metadata included - carries two OMOPHub-specific headers that tell you which OMOP vocabulary release served the request:

Header	Example	Meaning
`X-Vocab-Release`	`2025.2`	Human-friendly release identifier
`X-Vocab-Release-Status`	`active`	Lifecycle status (`ready`, `active`, `deprecated`, `archived`)

Use these headers to confirm which release your client is actually hitting, especially when pinning a specific version via the X-Vocab-Release request header or vocab_release query parameter. See Vocabulary Versions for the full release history.

Content negotiation

GET /metadata respects the same Accept header rules as every other FHIR endpoint - JSON is returned by default; XML is served only when the client strictly prefers it. See the Content Type section of the overview for the q-value semantics.

Errors

HTTP	Issue Code	Cause
401	`login`	Missing or invalid API key

FHIR Terminology Service

​Overview

​Request

​Version variants

​Response

​Response headers

​Content negotiation

​Errors

​See Also