There's an argument running about MCP right now. You've probably seen it: a 400-point thread called "MCP is dead?" with real token numbers in it, four connected servers eating 21,077 tokens of context before anyone asks a question. The argument is about what MCP costs. Almost nobody in it has measured what agents actually do with the data a tool returns.
I ended up measuring that, not because I planned to, but because a maintainer refused to let me guess.
The question nobody wanted to answer with opinions
I contribute to CNCF Jaeger's MCP server. Last April I proposed exposing service performance metrics (latencies, call rates, error rates) as an MCP tool, and hit an immediate design fork: what shape should the output be?
Option one, summary rows: pre-aggregated stats per service, compact, cheap. Option two, per-bucket time series: the raw points, roughly 720 of them per service at default resolution, expensive but complete.
