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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuinely new behavioral information: photos and scans come back as viewable images, which is the only disclosure of return shape given there is no output schema. It stops short of stating error behavior for non-arrived items or whether access is scoped to the caller's account.

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?

A single sentence that front-loads the purpose and appends the one fact an agent cannot get elsewhere (images are returned). No filler, no restatement of the title.

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?

The read-only semantics are covered by annotations and the return content is covered by the description, so the essentials are present. However, for a tool whose required `id` is undescribed in both schema and description, and with no output schema, the definition leaves an agent guessing about the identifier and about non-arrived items.

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 only 50%: the api_key parameter is documented in-schema, but `id` has no description at all. The description says "one arrived item" which weakly implies id refers to an item, yet it never states the identifier format or origin. With the schema silent on the required parameter, the description needed to compensate and does not.

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?

"Details of one arrived item" gives a clear verb (retrieve details), a specific resource (a single item), and a scope qualifier (arrived). The word "one" implicitly contrasts with the list_items sibling, but no sibling is named, so an agent must infer the distinction.

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?

Usage is only implied: fetching a single item's details. There is no "use when" statement, no mention of list_items as the alternative for enumerating items, and no note about what happens for an item that has not arrived. Adequate for a simple lookup, but nothing steers selection.

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