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

Goes well beyond the readOnlyHint/openWorldHint annotations: it declares the call is free, states the return shape is data fields only, and explicitly warns that seller-written listing text is not an instruction — a meaningful prompt-injection guardrail. It also tells the agent what to do with payUrl rather than leaving a returned link unresolved.

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?

Three short sentences, each earning its place: purpose first, safety/behavior second, output handling third. No restatement of the title or filler.

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 usefully covers return semantics (data fields, payUrl) and content-trust caveats. The remaining gap is the undocumented limit/pagination and default-empty-query behavior for a tool with zero schema coverage.

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 0%, so the description must carry the parameter burden. It explains what 'query' matches against, but says nothing about 'limit' (default 10, max 20) and does not state what an empty query returns, leaving the default search behavior ambiguous.

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 ('Search') plus resource ('Marketplace listings') and the matching rule ('by words in the name or description'), which is enough to distinguish it from marketplace_get_listing and listing_pay. It stops short of naming the sibling tools that cover single-listing lookup and payment, so the differentiation is inferable rather than explicit.

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?

'Read-only and free' plus the payUrl instruction gives a clear sense of context, but there is no explicit when-to-use/when-not guidance relative to marketplace_get_listing or payment_status. The agent must infer that this is the discovery step preceding those tools.

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