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

Annotations already declare readOnlyHint=true and openWorldHint=true, and the description is consistent with both. It adds valuable behavioral context beyond the annotations: the 3-credit cost per request, the sampling semantics ('Points are movements, not poll ticks... recorded when the price or status changed, or once every 24 hours'), and the coverage model. No contradiction with annotations.

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?

Five sentences, each earning its place: core purpose and ordering, cost, sampling semantics, coverage limitation, and the explicit scope caveat. The most important info is front-loaded in the first sentence, and no sentence is redundant with the schema or annotations.

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?

Comprehensive for a read-only lookup tool with 100% schema coverage. It explains the return concept (points), cost, coverage limitations, and ordering. The only minor gap is that with no output schema, it does not detail the exact response shape, but the 'points' explanation substantially compensates for that.

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 baseline is 3. The description adds real meaning by defining what a 'point' is (a movement or a 24-hour tick), which enriches understanding of the limit, from, and to parameters — clarifying that limit counts movements and that from/to bound observedAt events. This goes beyond the schema's bare parameter definitions.

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 and resource: 'Get every price and status Nephia observed for one Vinted listing.' It clearly scopes to a single listing and is readily distinguishable from sibling vinted_market_stats (market-level data) and the query/analysis tools. The 'oldest first' ordering and per-listing scope leave no ambiguity about what this tool does.

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?

Provides clear context: it is a per-listing history tool with explicit limitations ('Coverage grows with usage... only for items that appeared in a search Nephia observed' and 'This is not a complete index of Vinted'). This implies when it is appropriate, though it stops short of naming specific alternative tools or explicit when-not-to-use exclusions.

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