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

Annotations already cover the safety profile (readOnly, openWorld, non-destructive), yet the description adds substantial extra behavior: the exactMatches=false plus notice fallback for loosely-related suggestions, and the billing model (per-result-page units, keep max_results modest). This is real context beyond the structured fields.

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?

Front-loaded with purpose and return shape, then filters, then the exactMatches caveat and billing. Dense but every sentence carries information; the enumeration of return fields is slightly list-heavy but justified since no output schema exists.

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 13-parameter tool with no output schema, the description adequately covers both input groups and the response shape, and it flags the non-obvious eBay fallback behavior that would otherwise mislead an agent. Nothing essential to correct invocation appears missing.

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 description coverage is 100%, so the schema already documents all 13 parameters including defaults and the marketplace enum list. The description restates the filter/sort/paging groups but adds no syntax or format detail beyond the schema, so the baseline 3 applies. It also references a 'max_results' knob that does not exist in the schema, a minor inconsistency.

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 verb (searches) and resource (eBay listings), names the scope (any regional marketplace), and enumerates the exact return fields including normalised conditionCode. An agent can distinguish this from amazon_search or walmart_search purely from the definition since it is explicitly eBay-scoped.

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?

Gives clear context for marketplace selection ('prices, currency and availability differ between ebay.com, ebay.de, ebay.co.uk') and how filtering/sorting/paging work. It never states when NOT to use this tool or points to a sibling alternative, so it stops short of a 5.

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