We propose to investigate AgFBF4, compound known for > 20 years, with inelastic neutron scattering. The scope is to determine the value of J for this Ag(2+)-based 1D antiferromagnet, which shows the shortest Ag-F bond length ever measured (30% larger than that measured for Sr2CuO3. The J values are usually reproduced with satisfactory accuracy at this level of calculations, for example the value computed for Sr2CuO3 is -253 meV (thus overestimated by < 5%). If our theoretical result is confirmed by experiment, fluoroargentates(II) would outperform isoelectronic oxocuprates(II) and rank second to none as far as the absolute value of J via 1 atom is considered. Simultaneously, AgFBF4 should be even more close to perfect 1D behaviour than Sr2CuO3.