What it requires. A topic scope or action description a competent reader could not act on without outside knowledge: unstated abbreviations, internal process names, or an instruction whose success condition is not stated.
Why it matters. The provider's own standard is better than any threshold we would invent: put yourself in the model's shoes, and ask whether it is obvious how to use this tool from the description and parameters alone. This is irreducibly semantic and is reported as a judgement rather than a measurement. A related shape is worth naming: a sequencing constraint stated only as an instruction - "call X before Y" - is a hope, not a control.
How to fix it. Rewrite the instruction so its success condition is stated and its terms are defined in it. Where the constraint must hold, enforce it in the action rather than asking for it.
Source. Anthropic tool-description guidance
Is this rule worth checking?
Votes and comments are published here. We read them, and we publish what we change with the reasoning — a vote does not move a rule on its own.