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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so safety and idempotency are covered structurally. The description adds real value by disclosing the response payload — question, balance-of-evidence line, MeSH terms, area, citation string, and nested card fields — which is otherwise absent since there is no output schema. It stops short of covering failure behavior for an invalid number.

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 short sentences, no filler, with the identifying scope front-loaded before the return-value summary. Every clause carries information an agent would otherwise have to guess.

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 one-parameter read tool with full annotations and no output schema, the description does the essential work of explaining what comes back, including nested card contents. The only meaningful gap is what happens when the permanent number does not exist.

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% and the single parameter 'n' is already documented with an example value. The description reinforces that the number is 'permanent' (stable, not a transient search rank), which is a small but genuine addition; baseline 3 applies when the schema carries the detail.

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 states a specific verb and resource — 'Get one SourceMed shelf in full by its permanent number' — and enumerates the returned content. It is clearly a single-record fetch, but it never names list_shelves or search_shelves as the alternative, so sibling differentiation is left to inference.

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?

'By its permanent number' implies the precondition that you already have a stable identifier, which hints at when to use it over search_shelves. However, there is no explicit when-to-use or when-not-to-use statement, and no guidance on how to obtain the number if unknown.

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