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

Annotations only declare readOnlyHint and openWorldHint, so the description carries the rest: it discloses the window sizes, the per-condition/printing/language breakdown, and that each period reports market price, quantity sold, transaction count, low/high sale price and average daily sales volume. It says nothing about historical data limits, coverage gaps, or pagination, so it adds useful but incomplete behavioral context.

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 what is fetched and scoped by product id, followed by the metric list and the use case. The long colon-delimited enumeration is dense but mostly earns its place, though it partly duplicates the output schema.

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 an output schema present, the description need not explain return formatting, and annotations cover the read-only safety profile. What remains missing is minor: no note on data availability or how far back history goes, but nothing critical for correct invocation is absent.

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% and both parameters are already documented in the schema, including the default of 'quarter' and the four window values. The description restates those same window options without adding syntax, constraints, or edge cases, so the schema does the heavy lifting.

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 one TCGplayer product's price history'), plus the granularity (per condition, printing, language) and the exact metrics returned. It's clearly distinguished in practice from tcgplayer_sales and tcgplayer_price_guide, but it never names those siblings explicitly, leaving the agent to infer the boundary.

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?

'Use this to see how a card's price has trended' gives one legitimate use case (trend/time-series analysis), and the required product id is implied to come from tcgplayer_search. There are no exclusions or explicit alternatives, so when-not-to-use is left to inference.

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