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

Even with readOnlyHint and openWorldHint annotations, the description goes well beyond them by disclosing credit cost, soldRate being always null due to missing sold detection, coverage being tied to observed searches, and explicitly stating this is not a complete index. This is high-value behavioral transparency that materially prevents misinterpretation.

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?

Four sentences, each earning its place: output summary, cost, date constraints, soldRate caveat, and coverage caveat. The core result type is front-loaded, and there is no filler or repetition of schema details.

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 read-only stats tool with no output schema, the description covers the essential invocation semantics: optional filters, defaults, range limits, cost, ordering, and a critical null field caveat. It is slightly incomplete only in that it doesn't describe the full response shape beyond the listed aggregates, but nothing needed to decide whether to call it is 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 coverage is 100%, so the baseline is 3. The description adds meaningful constraints not present in the schema: the default 30-day range, the 365-day maximum range, and 'newest first' ordering. It also names the filterable dimensions in plain language, reinforcing the schema without fully duplicating it.

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 clearly states a specific resource (Vinted market), specific outputs (p25/median/p75 and per-day listing count), and a precise verb ('Get'). It also conveys scope and filtering. However, it does not explicitly differentiate this tool from related siblings like vinted_price_history, so it stops short of full sibling differentiation.

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?

The description provides strong usage constraints: 5 credits per request, default 30-day window, 365-day maximum, soldRate always null, and coverage limitations. It does not explicitly say when to choose this tool over alternatives, nor does it name sibling tools, so the usage context is implied rather than directly guided.

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