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There are currently approximately 31 species of Micrathena for Central America alone. I love how people typically say M.sagittata or M.gracilis, but what about all the rest??!? This one seems most like Micrathena zilchi, but not recorded south of Honduras/El Salvador, so is quite an expansion of range into Costa Rica.
This is not a tarantula, but an very important one to recognise, the Wandering spider Phoneutria sp. (family Ctenidae). Based on your location P. boliviensis might be most likely but also P. fera and P. reidyi are quite possible. A ventral photograph of markings under the abdomen would have helped make a species identification. BUT please take care with these spiders, the venom can be medically significant.