There is no spreadsheet import yet. For bulk onboarding use the external API (POST /employees with the employees:write scope) or the manual form, one by one.
What exists today
File import (CSV or Excel) is not available in the interface yet. The two ways to add employees are the Employees > New form, one at a time, and the external API, which accepts creating employees in sequence from a system of yours.
Bulk onboarding through the API
Create an API key with the employees:write scope under API keys and call POST /employees once per employee, with the same fields as the form (name, ID, email, position, department, contract type, hire date, salary, currency). Department and position ids come from GET /departments and GET /positions. The limit is 100 requests per minute per key, enough to onboard a whole team in a few minutes.
The OpenAPI specification is at /openapi.json and the interactive reference is on the API documentation page.
Validation
Both the form and the API validate the fields before saving and return the error per field (invalid ID, duplicate email, unknown department). Nothing is half-saved: a request with an error does not create the employee.