List object storage units

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds useful domain context (units own buckets and access keys) and a null-semantics note, but the note concerns maxBuckets/limitKb, which appear nowhere in the input schema, so its behavioral value is unclear rather than additive.

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?

Three short sentences, front-loaded with the core action, which is good. However, the closing 'A null maxBuckets or limitKb means unlimited' is unearned in this context: those identifiers are absent from the schema, so the sentence spends space on ambiguous, unexplained references.

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 simple three-param read with rich annotations, the definition covers the domain model but not the shape of a returned unit or how 'usage figures' appear in the response. With no output schema, a brief note on what a unit record contains (the very maxBuckets/limitKb fields it alludes to) would have closed the gap.

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 page, usage, and pageSize are fully documented upstream; the description only echoes 'optionally with usage figures' for the usage flag. The maxBuckets/limitKb sentence does not correspond to any input parameter, so it adds no parameter-level meaning and risks making an agent search for fields that aren't there.

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?

Specific verb+resource: 'List your S3-compatible object storage units, optionally with usage figures.' The sentence 'A unit contains buckets and has its own access keys' implicitly separates this from siblings like list_object_storage_buckets and list_object_storage_access_keys by establishing the containment hierarchy, though it never names those siblings directly.

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?

No explicit when-to-use vs when-not guidance and no named alternatives. The only routing signal is the implied hierarchy ('a unit contains buckets') and the optional 'usage figures' flag, which leaves the agent to infer that this is the top-level listing call for object storage.

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