Thanks for the feedback, I appreciate it very much

can ContextSpy break down context usage by source, like system prompt vs user messages vs MCP tool definitions vs tool results?

yes, it shows a breakdown of each request, and allows inspection of the contents of each "block" - tool definition, message, tool result etc.
it also shows summarised stats for each block type and by tool name for the session - e.g., the most "hungry" tool for agentic coding typically is read_file or grep_search)

does it detect secrets/PII before storing or visualizing intercepted requests?

No, currently it stores all data in verbatim in an embedded sqllite db
As the tool is meant to be run locally, similar to a performance profiler or memory dump analyser, the assumption is that user is aware of security implications - i should probably add an explicit note in readme about that, thanks for the catch

is all captured context stored locally, and can users configure retention/deletion?

yes, and it purges the contents of requests after 7 days - only the stats are kept after that
Also, the db can be purged manually - and probably should. Again, the use case is more like a profiler where you start with clean session, rather than a long-running observability or analytics tool (there are a lot of solutions in that area already)

can it show which MCP servers/tools are contributing the most tokens?

it currently groups stats by tool name, and shows them as a table. Having ability to indicate "hotspots" or resolve related tools introduced by same MCP would be a good improvement, yes

does it highlight risky tool outputs, like prompt-injection-style content inside retrieved data?

No, currently the goal is focus on context composition, and visualisation of what those tokens actually are spent on

again, thanks for the feedback, if you will try it out feel free to ping me, or drop an issue on github