Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description still adds real behavioral context beyond the annotations: recursive depth semantics and the critical trailing-slash pitfall where an unslashed prefix over-matches and yields a count delete_prefix would not act on.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, zero filler. The measure outputs are front-loaded and the delete_prefix/slash caveat follows, so the most decision-relevant content lands first.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a read-only measurement tool with no output schema, the description names what is returned (count, bytes, newest, largest) and warns about the one prefix pitfall that would produce a misleading answer. Nothing needed to call it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, and the schema already documents 'prefix' (including empty = whole bucket). The description goes beyond it by explaining the trailing-slash matching semantics for the prefix parameter, adding genuine meaning the schema does not convey.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description gives a specific verb (measure/count) and resource (objects under a prefix) and enumerates the exact outputs: object count, total bytes, newest and largest. It distinguishes itself from siblings like measure_bucket and list_objects by stating 'at any depth' under a prefix.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It names a concrete trigger ('Call it before delete_prefix to tell the user what would be destroyed') and names the alternative tool to pair it with. It also gives an explicit when-to-do-something-different rule for the trailing slash, which is precisely the kind of routing guidance an agent needs.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.