According to the grugq, one of the baddest dudes on the internet, no, you can't be an APT just because you built a custom tool.
Read this, and believe every word of it. https://medium.com/@thegrugq/cyber-ignore-the-penetration-testers-900e76a49500
To sum it up "you can't download your way to parity with Fort Meade", as said by the incomparable @Marasawr.
(Fun fact, Marasawr once judged a policy competition I was in. I got out of my depth technically, thinking I could get away with it in a policy setting, and they dismantled my position and mercifully allowed me to get back to more defensible ground. The other judges didn't know/realize what had happened.)
Respectfully Marasawr, you didn't specify what part of Fort Meade. Here at Hopper's Roppers, we're shooting for parity with a Mexican place named Rinconcito Mexicano that has a great margarita menu and above average tacos.
Time to go be an APT. * Cue Rocky music and a slow motion montage *