◇ Could this help me?
Yes for the add-ons, no for the install method. Three of the four address real and well-known failure modes: a documentation server fixes generated code written against a remembered version of a library, a planning layer reduces the number of changes made without a plan, and a simplifier counteracts a genuine tendency toward unnecessary abstraction. The part to reject outright is the instruction to ask the agent to go find the repository and install it, because a package resolved from a spoken name with no source is exactly the attack that name-squatting relies on, and an agent is a poor judge of which repository is the real one. What to do instead: install from the official marketplace where a listing exists, and for anything else identify the canonical source and confirm the publisher before installing. General practice.
I am considering four additions to my coding agent setup: a sequential-thinking tool server, a spec-driven planning plugin, a current-library-documentation server, and a code simplifier. For each one, research it before anything is installed: name the canonical repository or marketplace listing, who publishes and maintains it, how widely it is used, what permissions or access it requests, and whether there are similarly named packages that could be confused with it. Present all of that to me as findings, and install nothing until I explicitly approve it. Then recommend which single one to add first and what I should measure to tell whether it actually helped.