You’re supposed to let others know, to avoid secret negotiations and violations of the Logan Act.
Via Politico:
Democratic Rep. Tulsi Gabbard went on a secret trip to Syria this week without telling congressional leaders beforehand, according to multiple sources.
Aides confirmed that House Speaker Paul Ryan (R-Wis.) and House Minority Leader Nancy Pelosi (D-Calif.) weren’t given any advance warning before the Hawaii Democrat visited the Middle East on a trip that was not government-sanctioned travel. Informing leaders of such travel is standard and expected practice.
Emily Latimer, a spokeswoman for Gabbard, described the trip, first reported by Foreign Policy, as a “fact finding” visit to Syria and Lebanon. Latimer would not say whether Gabbard met with Syrian President Bashar Assad, citing “security reasons.”