Success:

200: OK. Returns CSV contents of the contacts.

optins,Opt-In Count,ContactID,CampaignID,Tags,First Name,Last Name,Full name,Phone Number,Email,Street,City,County,State,Zipcode,Country,URL,Icon,Source,Notes,Question,Custom1,Custom2,Custom3,Custom4,Custom5,Date Created,Date Last Updated,Belongs to Group,Contacted Count,Reply Count,Last Skipped Project,Last Skipped Date,Last Skip Reason,Skipped in Projects,Delivery Error Count,Opt-Out Count,Last Activity Date,Undelivered in Projects,Transferred from,Last Pause Date,Hubspot ID,State Voter ID,L2 Voter ID,L2 Tags,L2 First Sync Time,L2 Last Sync Time,WinRed Last Donation Time,WinRed Last 5 Donations Dates,WinRed Text Donated Amount,# of WinRed Text Donations,# of WinRed Errors,Last WinRed Error,# of WinRed Form Donations,WinRed Form Donated Amount,WinRed Donor ID
,,7245934627,c_ghcilhywy6mz,landline,Dr. Smith,Smith,Dr. Smith Smith,7245934627,,,,,,,,,,,,,,,,,,2025-02-04 03:01:08 GMT-0000,2025-02-04 03:14:05 GMT-0000,"45,47",,,,,,,,,2025-02-04 20:07:07 GMT-0000,,,,,,,,,,,,,,,,,,
,,8144232030,c_ghytiepefnzgy6mz,,Dr. Bones,James,Dr. James Bones,8144232030,,,,,,,,,,,,,,,,,,2025-02-04 03:04:41 GMT-0000,2025-02-04 03:14:05 GMT-0000,"46,47",1,,,,,,0,,2025-02-04 20:06:51 GMT-0000,,,,,,,,,,,,,,,,,,

The response header Content-Type is text/csv.

Errors:

401: Unauthorized. If the authentication failed is returned, either the username or password is incorrect. Verify the both from the applications Integrations / API Keys for your account in the application.
400: Bad Request. With a code of LIMIT: Downloading contacts has limits, how may can be directly downloaded and how many can be downloaded via reports, this error will explain the limitations depending on your query