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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds useful return-shape detail (paginated items with title, set number, condition, price, availability, URL) but says nothing about total counts, page limits beyond schema, or empty-result behavior.

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 sentences, front-loaded with purpose then return shape. No filler. Slightly compressed to the point where filter interaction details are omitted, but structurally clean.

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?

A read-only search tool with full schema documentation and no output schema; the description covers purpose and return fields, which is sufficient. Missing only edge-case behavior (empty query results, pagination limits) that would help an agent loop through pages.

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 per-parameter descriptions and enums, so the schema carries the semantics. The description only summarizes filter categories (category, theme, condition, USD price) without adding meaning beyond the schema, which matches the baseline 3.

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 ("Search public LEGO listings") plus the searchable fields and the return contents. It distinguishes itself from siblings like check_availability and quote_shipping implicitly, but doesn't name them or explain the boundary explicitly.

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 — search listings, then presumably use check_availability or quote_shipping for follow-ups — but no explicit when-to-use/when-not or alternative routing is stated. An agent must infer the workflow from sibling names alone.

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