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Measuring tool-call reliability at 41M calls a month

What we track, what we ignore, and the one chart that predicts incidents a day early.

Dev RamanSep 18, 2026 ยท 7 min readXin
fig. 01 / coverdemo

Reliability is not one number. We track three: schema rejects, retries, and silent successes that a verify step later fails.

The one chart

Retries per thousand calls, by tool. When a line bends up, an incident follows within a day.