Step 1 of 2. Sends an OTP to the mobile number linked to the given Aadhaar number and returns a session_id. Pass that session_id, plus the OTP the user receives, to /v2/verify/okyc_get_result to complete the verification.

Response contract: a successful send returns HTTP 200 with status: "success", error_code: null, and data.session_id populated. A definitive invalid-Aadhaar result ALSO returns HTTP 200 with status: "success", but carries a non-null error_code and data: null: every 2xx response is status: "success", so do NOT distinguish a full-success verdict from an invalid one by status; branch on error_code (null = OTP sent, a non-null IDTO_2xx = invalid). Only a raised error returns status: "error". Every response carries billed (whether the call was charged). Authenticate with your X-Client-ID and X-API-KEY headers.

Codes: IDTO_202 (2xx, invalid Aadhaar number), IDTO_001 (empty or malformed Aadhaar number; 400, or 422 if the request body fails schema validation), IDTO_005 (user consent required, 400), IDTO_004 (duplicate verification reference, 409), IDTO_009 (insufficient credits, 402), IDTO_006 (rate limited, 429), IDTO_007 (config error, 500), IDTO_008 (service busy, 503).