The 23-year old Spanish winger, who can operate on the left side of midfield or in defence, will be added to Sporting's 2014 MLS squad on an international roster spot upon receipt of his International Transfer Certificate and P-1 Visa.
SKC head coach Peter Vermes was delighted to welcome Toni to Sporting Park after most of his senior career with Celta.
"We are happy to be able to add a player of his quality to our roster," Vermes said in an official statement.
"He can play multiple positions within our system and we hope that we can help him to adapt to our team and to Major League Soccer as quickly as possible."
Toni, who made close to 80 appearances for Os Celticos and 16 during a loan spell with Huesca in 2011, was thrilled to be embarking on a new chapter in his career.
"I am very excited to be in Kansas City," Dovale said.
"Sporting KC is a very ambitious and successful club and I look forward to helping them achieve their goals. My motivation is high to come here and improve as a player and help this club any way possible."
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