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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds genuinely non-obvious behavior: results are cached for 15 minutes, and `skins` is a capped preview of 24 with `skins_total` giving the full count. It does not say what happens for an unknown shortname, but the added context is solid.

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?

The core purpose is front-loaded in the first sentence and field enumeration follows logically. The long parenthetical list of response fields is dense but every element earns its place given there is no output schema; minor tightening is possible.

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?

With no output schema, the description carries the full burden of describing the return shape, and it does so field by field — including ordering semantics ('highest chance first'), units (USD cents, chance_pct), and the capped-preview-plus-total pattern for skins. Nothing material is missing for a one-parameter read tool.

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% with an example (`rifle.ak`) already in the schema, so the description's only added signal is the incidental `/items/{shortname}/skins` reference, which confirms shortname is used as a path segment in related routes. Baseline 3 applies when the schema does the heavy lifting.

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 resource and scope ('Full item detail bundle. Everything the item page shows, in one response') and enumerates the payload, so an agent knows exactly what this returns. It does not explicitly contrast itself with search_items/browse_items or get_item_skins, so sibling differentiation is only implied via the skins paging pointer.

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 implied by the description's scope — comprehensive single-item lookup keyed by shortname — but there is no explicit when-to-use or when-not guidance versus search_items, browse_items, or get_item_skins. The one routing hint is a pointer to `/items/{shortname}/skins` for the full skins list.

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