You need to provide agentic tools with enough context about the project so they can find their way around. In Claude Code this is typically done via a CLAUDE.md document at the root of the codebase.

I work on Chromium and my experience improved immensely by using a detailed context document (~3,000 words) with all sorts of relevant information, from the software architecture and folder organisation to the C++ coding style.

(The first draft of that document was created by Claude itself from the project documentation.)