My thoughts are in blue, words to delete are in red, suggested rephrasing is in orange.

GERALD FRANCIS FINN (“Finn”) You only capitalize character names in a synopsis, not in a query is a trained fighter and enforcer who is he fighting? What is he enforcing? on the planet CARON, that was founded by the ultra-wealthy alien KERET as a haven from restrictive institutions. Finn has both seen and lived the bottom and the top of Caron society and is torn between the Caron cultural imperative of self-serving achievement, versus his intense sense of honesty and caring for others. Finn also has an impulse to action that does not always turn out as expected. What does that mean? This entire paragraph is just setting up his personality, and we have no indication of plot

When Finn’s friend LOUISE REYNOLDS is killed, his investigation uncovers deceptions and cross-purposes, and finally the apparent killer: Louise’ lover TRISTAN HELSING. Overcome by grief for his friend, Finn rushes to confront Helsing and kills him in a duel. This is reading much more like a synopsis than a query. A query needs to establish what the main character wants, what stands in their way of getting it, and what they will do in order to overcome the obstacles. This isn't doing that. It's walking through the plot points, which is the job of a synopsis, not a query

Finn thinks the mystery is solved, until Finn’s mentor WILL MACHADO accuses Finn of being the real murderer. Finn escapes and turns to his enemy, the Phair MAYHAN DEL CARRA. With Del Carra’s help Finn learns that Machado is plotting to take control of the robotic SENTRIES, the only advanced weapons on the planet. If Finn fails to stop Machado, one faction will gain total power, obliterating the few scraps of freedom that exist on Caron. How does all of this tie together? How does this plot interact with his character? What does he want? What's standing in his way? What does the murder have to with anything?

Finn’s story, STONE BY STONE, is a science fiction novel of 98,000 words. The title is inspired by Finn’s father, Charlie. A master mason, Charlie worked to build splendid buildings for the rulers of Caron. The story of Charlie’s life, and death, animates all the actions and feelings of his son. This isn't relevant information in a query. An agent doesn't really care what the title means or what the idea behind it is, and the fact that it's tied to the father of the main character means even less becuase they aren't part of the story. You need to use every bit of space you have to illustrate what Finn wants, what stands in his way, and what will he do to overcome that?

A book similar to STONE BY STONE is PROVENANCE by Ann Leckie, a 2018 Hugo nominee that explores intrigue and coming-of-age themes against the backdrop of a ruthless culture. Another would be PLANETFALL by Emma Newman, a 2020 Hugo nominee for best series, where a tale of mystery unfolds on a bootstrapping colony world. How is coming of age similar to what you have here? Is this culture ruthless? We don't have any indication of what's going here other than there's a guy who is nice but realizes that won't get him ahead, his friend dies, somebody betrays him, and now a bad person is trying to take over weapons of mass destruction. Right now the culture isn't present on the page, the murder doesn't feel like it ties to the larger plot, and there's no sense of what Finn will / is going to do in order to stop the bad guy, or what is at stake if he doesn't.

About me, I am a member of the SFWA, have workshopped my writing with Craig Shaw Gardner and Jeff Carver, and have self-published four books. Unless these have really good sales numbers, I wouldn't mention them I have worked as a scientist, co-authoring papers for peer-reviewed journals. For ten years I intensively studied, and taught, the martial art Aikido. Later I worked in tech for cloud startups and companies including IBM where I achieved the title of Distinguished Engineer.