openapi: 3.1.0
info:
  title: Community Health Systems Patient Access API
  description: >-
    Community Health Systems provides healthcare interoperability APIs
    pursuant to the CMS Interoperability and Patient Access Final Rule
    (CMS-9115-F). The Patient Access API allows third-party applications
    to retrieve data concerning adjudicated claims, encounters, formulary
    data, and clinical data using FHIR standards.
  version: '2026-01-01'
  contact:
    name: Community Health Systems
    url: https://www.chs.net
externalDocs:
  description: CMS Interoperability Final Rule
  url: https://www.cms.gov/regulations-and-guidance/guidance/interoperability/index
servers:
  - url: https://api.chs.net/fhir/r4
    description: FHIR R4 Production Server
tags:
  - name: Claims
    description: Adjudicated claims and encounter data
  - name: Formulary
    description: Formulary and medication data
  - name: Patient
    description: Patient demographic and clinical data
  - name: Practitioner
    description: Provider information
security:
  - oauth2: []
paths:
  /Patient:
    get:
      operationId: searchPatients
      summary: Search patients
      description: Search for patient records using FHIR Patient resource.
      tags:
        - Patient
      parameters:
        - name: family
          in: query
          schema:
            type: string
        - name: given
          in: query
          schema:
            type: string
        - name: birthdate
          in: query
          schema:
            type: string
            format: date
      responses:
        '200':
          description: FHIR Bundle of Patient resources
          content:
            application/fhir+json:
              schema:
                $ref: '#/components/schemas/Bundle'
        '401':
          description: Unauthorized
  /ExplanationOfBenefit:
    get:
      operationId: searchClaims
      summary: Search claims
      description: Retrieve adjudicated claims data as ExplanationOfBenefit resources.
      tags:
        - Claims
      parameters:
        - name: patient
          in: query
          required: true
          schema:
            type: string
      responses:
        '200':
          description: FHIR Bundle of ExplanationOfBenefit resources
          content:
            application/fhir+json:
              schema:
                $ref: '#/components/schemas/Bundle'
  /MedicationKnowledge:
    get:
      operationId: searchFormulary
      summary: Search formulary
      description: Retrieve formulary and medication information.
      tags:
        - Formulary
      responses:
        '200':
          description: FHIR Bundle of MedicationKnowledge resources
          content:
            application/fhir+json:
              schema:
                $ref: '#/components/schemas/Bundle'
  /Practitioner:
    get:
      operationId: searchPractitioners
      summary: Search practitioners
      description: Search for provider directory information.
      tags:
        - Practitioner
      parameters:
        - name: name
          in: query
          schema:
            type: string
        - name: specialty
          in: query
          schema:
            type: string
      responses:
        '200':
          description: FHIR Bundle of Practitioner resources
          content:
            application/fhir+json:
              schema:
                $ref: '#/components/schemas/Bundle'
components:
  securitySchemes:
    oauth2:
      type: oauth2
      flows:
        authorizationCode:
          authorizationUrl: https://api.chs.net/oauth2/authorize
          tokenUrl: https://api.chs.net/oauth2/token
          scopes:
            patient/*.read: Read access to patient data
            launch/patient: Patient launch context
  schemas:
    Bundle:
      type: object
      properties:
        resourceType:
          type: string
          const: Bundle
        type:
          type: string
        total:
          type: integer
        entry:
          type: array
          items:
            type: object
            properties:
              resource:
                type: object