> ## Documentation Index > Fetch the complete documentation index at: https://developers.projectcor.com/llms.txt > Use this file to discover all available pages before exploring further. # Attach users to a contract > Attaches one or more users to a contract, each with one or more date ranges. ## OpenAPI ````yaml /api-reference/openapi.json post /contracts/{contract_id}/users openapi: 3.1.0 info: title: COR API description: >- The COR API lets you integrate with projectcor.com applications using simple HTTP methods, in either XML or JSON formats, making this an ideal API for developing integrations with other softwares, external clients or mobile applications version: 1.0.0 servers: - url: https://api.projectcor.com/v1 description: Production server security: - bearerAuth: [] paths: /contracts/{contract_id}/users: post: tags: - Contracts Users summary: Attach users to a contract description: >- Attaches one or more users to a contract, each with one or more date ranges. parameters: - name: contract_id in: path required: true schema: type: integer requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/ContractAttachUsersInput' example: users: - id: 123 dates: - start: '2026-01-01' end: '2026-02-01' - start: '2026-01-01' end: '2026-02-02' responses: '200': description: Users attached to contract with full or partial success content: application/json: schema: $ref: '#/components/schemas/ContractAttachUsersResponse' example: status: partial_success company_id: 999 contract_id: 777 records_received: 8 records_created: 2 records_rejected: 8 assigned: - id: 501 user_id: 88001 start_date: '2024-01-01T00:00:00.000Z' end_date: '2024-12-31T00:00:00.000Z' - id: 502 user_id: 88001 start_date: '2024-03-01T00:00:00.000Z' end_date: '2024-06-30T00:00:00.000Z' errors: - id: 88001 dates: - start: '2024-06-01' end: '2024-04-01' message: Date malformatted. Start date must be before end date - start: null end: null message: Date malformatted - start: '2024-02-01' end: null message: Date malformatted. Start and end date are required - start: not-a-date end: '2024-12-31' message: Invalid date - start: '1990-01-01' end: '1990-06-30' message: >- Invalid contract periods. Range must be within contract start and end dates message: Partial success. Some dates were rejected - id: hello dates: - start: '2024-01-01' end: '2024-12-31' message: User malformatted - id: 88002 start: '2024-01-01' end: '2024-12-31' message: >- Legacy format detected. Use "dates" array instead of "start" and "end" fields - id: 88003 dates: [] message: Date malformatted or empty - id: 88004 dates: - start: '2024-07-01' end: '2024-07-01' message: Date malformatted. Start date must be before end date message: Dates are malformatted or empty - id: 88005 dates: - start: null end: null message: Date malformatted message: Partial success. Some dates were rejected - id: 999999 dates: - start: '2024-01-01' end: '2024-12-31' message: User malformatted - id: 88005 dates: - start: '2024-01-01' end: '2024-06-30' message: User malformatted components: schemas: ContractAttachUsersInput: type: object required: - users properties: users: type: array items: $ref: '#/components/schemas/ContractAttachUsersUserInput' ContractAttachUsersResponse: type: object properties: status: type: string enum: - success - partial_success - failure description: Result status for attach operation company_id: type: integer description: Company ID contract_id: type: integer description: Contract ID records_received: type: integer description: Total number of date records received records_created: type: integer description: Total number of date records successfully created records_rejected: type: integer description: Total number of date records rejected user_ids: type: array items: type: integer description: Array of user IDs that were successfully assigned to the contract assigned: type: array items: $ref: '#/components/schemas/ContractUserAssignment' description: Array of user assignments for the contract errors: type: array items: $ref: '#/components/schemas/ContractAttachUsersError' description: Array of user assignments that failed to be assigned to the contract ContractAttachUsersUserInput: type: object required: - id - dates properties: id: type: integer description: User ID dates: type: array description: Date ranges to assign for the user items: $ref: '#/components/schemas/ContractAttachUsersDateInput' ContractUserAssignment: type: object properties: id: type: integer description: Assignment ID user_id: type: integer description: User ID contract_id: type: integer description: Contract ID company_id: type: integer description: Company ID start_date: type: string format: date-time description: Assignment start date-time end_date: type: string format: date-time description: Assignment end date-time ContractAttachUsersError: type: object properties: id: type: - integer - string description: User ID that contains rejected dates dates: type: array items: $ref: '#/components/schemas/ContractAttachUsersErrorDate' start: type: - string - 'null' format: date description: Legacy start date field used in malformed payloads end: type: - string - 'null' format: date description: Legacy end date field used in malformed payloads message: type: string ContractAttachUsersDateInput: type: object required: - start - end properties: start: type: string format: date description: Assignment start date end: type: string format: date description: Assignment end date ContractAttachUsersErrorDate: type: object properties: start: type: - string - 'null' format: date end: type: - string - 'null' format: date message: type: string securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: JWT ````