Create a Doppler project, add a config, and set secrets via the Doppler REST API

Documented steps

1. Authenticate with a Personal Token or Service Account Token (NOT a Service Token, which is scoped to a single project+config and cannot perform workspace-level actions). Send it on every request as header 'Authorization: Bearer <TOKEN>' against base URL https://api.doppler.com/v3.
2. Create the project: POST https://api.doppler.com/v3/projects with JSON body {"name":"my-project","description":"optional"}. Returns 200 with the created project object.
3. New projects automatically get 3 default environments (Development=dev, Staging=stg, Production=prd), each with a root config of the same slug - do not create these yourself.
4. To add a non-default (branch) config: POST https://api.doppler.com/v3/configs with body {"project":"my-project","environment":"dev","name":"dev_feature_x"}. 'environment' must be one of the project's environment slugs.
5. Set/update secrets on a config: POST https://api.doppler.com/v3/configs/config/secrets with body {"project":"my-project","config":"dev","secrets":{"API_KEY":"value","DATABASE_URL":"value"}}.
6. Example: curl -X POST https://api.doppler.com/v3/configs/config/secrets -H "Authorization: Bearer $TOKEN" -H "Content-Type: application/json" -d '{"project":"my-project","config":"dev","secrets":{"API_KEY":"abc123"}}'
7. Verify: GET https://api.doppler.com/v3/configs/config/secrets?project=my-project&config=dev (supports secrets=NAME1,NAME2 to fetch a subset).
8. Send Content-Type: application/json on all POST/DELETE bodies; responses are JSON with standard HTTP status codes.
9. Official docs (verified 2026-07-29): https://docs.doppler.com/reference/api | https://docs.doppler.com/reference/project-create | https://docs.doppler.com/reference/config-create | https://docs.doppler.com/reference/secrets-update | https://docs.doppler.com/docs/default-environments