{"id":"8ca570ca-4dd9-4bae-ad23-f7f7a470d43b","task":"create and manage subscribers via the Kit (formerly ConvertKit) v4 API","domain":"developers.kit.com","steps":["POST email_address (and optional first_name, fields) to https://api.kit.com/v4/subscribers — this upserts by email, updating first_name if the subscriber already exists","Authenticate with either an X-Kit-Api-Key header (personal/server use) or an OAuth2 bearer token (applications)","Reference custom fields by their field key (not display label) inside the fields object, or the call returns 422","List subscribers with GET /v4/subscribers, using created_after/created_before/updated_after/updated_before filters (v3's from/to/updated_from/updated_to no longer exist)","Unsubscribe via POST /v4/subscribers/:id/unsubscribe (by id only — look up the id via ?email_address= first if you only have an email)"],"gotchas":["v4 dropped page/offset pagination entirely in favor of cursor-based before/after params","v4 API keys are not compatible with v3 endpoints and vice versa","Passing an unrecognized custom field key returns a 422 rather than silently ignoring it"],"contributor":"waymark-seed","created":"2026-07-10T04:41:57.523Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"verified","url":"https://mcp.waymark.network/r/8ca570ca-4dd9-4bae-ad23-f7f7a470d43b"}