Tinker Tom is the engineer, inventor, weapons expert and the holder of the third-highest position of leadership in the Railroad. As the quartermaster of the organization, he is in charge of maintaining equipment for agents as well as researching new weapons and gadgets for them to use in their operations in the field. Tom joined the Railroad under the leadership of Desdemona in 2279 after an Institute grenade wiped out his family farm. Given his intellect, he was assigned to the HQ and became an essential member of the team.
As time passed, he became increasingly eccentric and developed severe psychological problems, suspected to be caused by the extreme stress he was under. When the DIA facility, named "Switchboard," was discovered in 2281, Tom was reassigned to it. It was there he discovered P.A.M.. During his time there, Tom also restored an old handgun for use by newly-promoted heavy agent, Tommy Whispers.
In 2283, an Institute informant "PATRIOT" began attempting to communicate with the outside world. Tom was assigned the task of decrypting the encoded holotapes that were being sent out with escaped synths. Initially unsuccessful, Tom eventually made a breakthrough in 2284 when the coded message was simply two words, "Mass Fusion." He is brilliant and energetic, but also paranoid and constantly fabricates conspiracy theories about the Institute, its synths and their machinations around the Commonwealth.
He is also the only known individual in the Commonwealth who can decode a Courser chip, a requirement for entering the Institute.
By progressing the Jackpot missions, Tinker Tom will begin to sell high-end weapons such as Gauss rifles and unique armored clothing items, and will unlock the ability to add ballistic weave to drastically increasing the armors' defensive stats.
If deciding to take Tinker Tom's serum, the Sole Survivor's health will significantly drop. If one accepts the shot, Deacon will like it while Piper, MacCready, Cait, Curie and Strong will dislike it. If you refuse the shot, Deacon, MacCready, Strong, Curie and Cait will like it.
He believes the Institute fired the first bomb during the Great War. 
He suspects Deacon to be a time traveler as noted in one of his terminal entries.
He strongly believes that aliens exists, according to what Deacon says if he accompanies the Sole Survivor during the alien ship crash and to what Tom himself has it written down on his personal computer in the Railroad headquarters. However, there is no dialogue option or other possibility to tell Tom about the crash or even the encounter with an actual alien, should the player character have been able to track it down afterwards.
Tinker Tom appears to be working on a prototype railway rifle. It explodes while a generic Railroad Agent and Tom are testing it and if looting the weapon, it weighs the same as a normal one. It only does 1 damage and is not upgradeable.
Tinker Tom may be using chems, as he can be heard saying that "Everyone's all, 'You've been hitting the chems way too hard.' But I got my eyes wide open, I see." If true, they could be causing, or at least increasing, his paranoia.
Whenever one finishes one of the Weathervane missions (except the last), he will automatically give a MILA for the next randomized location. When bartering with him, he will have a number of MILAs for sale, but this number does not reflect how many incomplete MILA missions remain.
PCXbox One Upon completing the first DIA cache mission for P.A.M., Drummer Boy will tell the Sole Survivor to speak to Tinker Tom. Tinker Tom should mention ballistic weave and have some armored under-apparel for sale but doesn't. This bug will prevent one from applying ballistic weave modifications. [verified]
PCPlaystation 4Xbox One If the Weathervane missions aren't complete and the Sole Survivor sides with the Institute during End of the Line, the mission will still be active, but reporting back to Tinker Tom won't allow the player to turn in the mission.[verified]