ygo_get_card_price_trends

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

With no annotations, the description carries the full burden and does disclose an important data-semantics rule: per-printing prices exist only when the source reports set_price, and 0 means 'no price for that printing', not 'free'. That prevents a concrete misinterpretation. It says nothing about coverage gaps across markets or how missing markets are represented, which keeps it off a 5.

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 dense sentences, front-loaded with the returned content before the caveats and the alternative. No filler, though the first sentence is a long clause dump that could be split for scanning.

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 single-parameter read tool with no output schema, the description enumerates the return payload, flags the zero-price trap, and names the sibling for aggregate queries. The remaining gap is the 'trends' in the tool name — nothing explains whether any historical or directional price data is returned, which an agent answering a price-over-time question would need.

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% and the single parameter already documents 'Card name (English) or 8-digit passcode', so the baseline is 3. The description adds no further meaning — no ambiguity resolution between name and passcode lookups, no note on what happens when a name matches multiple cards.

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 enumerates concrete content — stats, text, printings, prices from TCGPlayer/Yuyu-tei OCG/Cardmarket AE, and Yugipedia links — so the agent knows this is a full single-card lookup. It falls short of 5 because the name promises 'price trends' yet no trend, history, or time-series data is mentioned, leaving a mild name/content mismatch an agent must reconcile.

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?

It explicitly routes ranking and 'most expensive / rising' questions to ygo_market_query, which is a real exclusion plus a named alternative. It lacks an explicit positive trigger ('use this when you need full detail on one known card'), so the when-to-use side is implied rather than stated.

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