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

Annotations declare destructiveHint=true/idempotentHint=false, and the description adds non-obvious behavior beyond them: the trailing-slash requirement, the destination-nonempty refusal, the one-object-per-request design, the smaller ceiling relative to delete_prefix, and early-stopping. It doesn't describe partial-copy state on early stop, which is the main residual gap.

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 dense sentences, front-loaded with the core action and layout semantics. The trailing phrase 'says so when it stops early' is slightly colloquial but carries a useful operational hint, so little is wasted.

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 destructive, no-output-schema mutation tool with full annotation coverage, the description covers the critical calling constraints (slash rules, overwrite, per-request copy, ceiling). What's missing is failure semantics—whether already-copied objects remain if it stops early—which an agent would want before invoking.

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, but the description adds real constraint meaning: prefixes must end in '/', overwrite governs the nonempty-destination case, and destination layout is preserved. This explains *why* the parameters matter rather than repeating their definitions.

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?

States a specific verb+resource ('Copies every object under a prefix to another prefix') and explicitly describes scope ('keeping the layout below it'), which cleanly separates it from the single-object copy_object and the move_prefix sibling.

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?

Gives a clear when-not condition ('Refuses to write into a destination that already holds objects unless overwrite is true') and comparative context against delete_prefix's ceiling. It stops short of naming the obvious alternatives (copy_object, move_prefix) or telling the agent when to prefer them, so it's clear context without explicit exclusions.

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