Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
prĕcātīvus, a, um, adj. [precor], prayed for, obtained by entreaty (postclass.): pax, Amm. 17, 5, 1: precativo modo, by prayer or entreaty, Ulp. Reg. tit. 24.
Adv.: prĕcātīvē, by request, by entreaty (post-class.), Ulp. Reg. tit. 25, 1 al.