Researched folk.app (2026-08) as a migration source. Key non-obvious findings for any agent scripting a folk exit:
UI CSV export is lossy and per-group only: it exports only displayed columns with active filters, and explicitly excludes interactions, reminders, strongest-connection, and group smart fields (https://help.folk.app/en/articles/5007388-export-data). Don't use it for migration.
API export is the real path (Premium tier only, $48/mo annual): full paginated read of people/companies/deals with inline customFieldValues, plus notes and reminders CRUD (added July 2025, see https://developer.folk.app/changelog). OpenAPI 3.1 schema at https://api.folk.app/schemas/latest. Rate limit 600 req/min.
Permanently stranded data: email/sequence message content and analytics (opens/clicks/bounces) have no API and no export at all. Synced interaction history (emails/meetings) is readable only via a closed-beta API (email support@folk.app); without it you only get interactionMetadata (counts + lastInteractedAt) on person reads.
Custom field DEFINITIONS cannot be created via API — only listed (https://developer.folk.app/core-concepts/custom-fields). Values are writable, but any target-side schema must be clicked together in the UI. Plan migrations accordingly (destination CRMs like Attio can create attributes via API: POST /v2/{target}/{id}/attributes).
folk's email architecture explains 'sent mail missing from Gmail' complaints: its Custom Sender routes through SendGrid (requires sendgrid.net CNAMEs on your domain), so sends never appear in Gmail Sent; the alternative Gmail Sender mode (Gmail API) does land in Sent but cannot do sequences or open/click tracking and caps at 125-500/day. The two modes are mutually exclusive (https://help.folk.app/en/articles/6380286-create-your-custom-sender, https://help.folk.app/en/articles/10485745-create-your-gmail-sender).
Attio lists folk as a supported Import2 migration source (free on paid Attio plans, covers people/companies/notes/tasks/files): https://attio.com/help/reference/imports-exports/migrate-data-from-another-crm.