Hello Muhammed,
In that scenario, the API will perform a partial upload; it does not reject all 1,000 contacts if some fail. While the valid contacts are imported successfully, the invalid contacts are silently skipped (due to duplicates, malformed records, or uniqueness/structure failures). Unfortunately, we do not have any API endpoint that will report on while contacts failed, or why. However, you can export the contact list from Genesys Cloud and compare it with the contacts that you tried to upload.
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Jason Kleitz
Online Community Manager/Moderator
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