Check Twitter Follow Relationship API

Numeric ID of the account whose following is checked. Send this or source_username.

Handle of the source account, as an alternative to source_user_id. Resolved to its ID first; an unknown handle returns a 404 and nothing is billed.

Numeric ID of the account being checked against. Send this or target_username.

Handle of the target account, as an alternative to target_user_id. Resolved to its ID first; an unknown handle returns a 404 and nothing is billed.

Comma-separated list of dotted field paths to keep in the response (one parameter, never repeated), applied to every object in the returned lists and to nested objects (for example fields=id,text,author.username; the list's own name may prefix a path, fields=tweets.id). A path prefix that lands on an array applies to each element (media.media_url_https). Pagination and envelope keys (next_cursor, cursor, has_more, count, partial, error, message, reason) are always kept. Unknown paths are ignored; up to 50 paths of up to 6 segments. Projection never changes status codes or billing, and applies to data reads only: account, feedback, session status, monitor (other than deliveries), webhook and stream-compat reads return their bodies unchanged.

Set to 1 (or true) to apply the built-in compact preset: ids, url, text, created_at, lang, the engagement counts, the is_retweet/is_reply/is_quote flags, conversation ids, the author's id/username/name/followers_count/verification, and the quoted or retweeted tweet's id/url/author username. The preset trims what it recognises and leaves alone what it would empty, so it never turns a body into {}. Combine with fields to add paths on top of the preset. Typically cuts a tweet page by 70 to 90 percent for LLM tool callers.