curl -X GET "https://api.omophub.com/v1/search/facets?query=diabetes&vocabularies=SNOMED,ICD10CM" \
  -H "Authorization: Bearer YOUR_API_KEY"

{
  "success": true,
  "data": {
    "query": "diabetes",
    "facets": {
      "vocabularies": [
        { "vocabulary_id": "SNOMED", "count": 245 },
        { "vocabulary_id": "ICD10CM", "count": 67 }
      ],
      "domains": [
        { "domain_id": "Condition", "count": 198 },
        { "domain_id": "Observation", "count": 87 },
        { "domain_id": "Drug", "count": 27 }
      ],
      "concept_classes": [
        { "concept_class_id": "Clinical Finding", "count": 156 },
        { "concept_class_id": "Disorder", "count": 87 },
        { "concept_class_id": "Procedure", "count": 42 }
      ],
      "standard_concepts": [
        { "standard_concept": "S", "count": 245 },
        { "standard_concept": "C", "count": 34 },
        { "standard_concept": "N", "count": 33 }
      ]
    }
  },
  "meta": {
    "request_id": "req_abc123",
    "vocab_release": "2025.1"
  }
}