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

Annotations already cover read-only, non-destructive and closed-world, so the description is not carrying the safety burden — but it adds genuine context beyond them: a hard cap of 10 results, cross-marketplace coverage (US, Japan-domestic, Chinese), USD normalization, and the fact that records are verified completed sales rather than listings. The privacy-logging note adds mild extra disclosure. Return format is left to the output schema.

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?

Front-loaded with the core purpose and returned fields, then supporting scope in the following sentences; three compact sentences with little waste. The trailing 'does not modify user data' clause largely restates readOnlyHint/destructiveHint=false, a small redundancy.

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?

An output schema exists, so return values need no further explanation, and the fixed cap of 10 removes any pagination question. Coverage of marketplaces and currency conversion is a useful plus. The only gap is the missing routing guidance relative to the pricing-history siblings, which is a usage issue rather than a completeness one.

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?

Only one parameter and schema description coverage is 100%, with the schema already stating that card_id comes from search_card / slang_lookup. The description reinforces the single-card scope but adds no new syntax, format, or constraint information about the parameter. Baseline 3 applies since the schema does the work.

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 ('most recent verified sales for one card') and enumerates returned fields (date, grading company + grade, USD price, marketplace), so the agent knows exactly what it gets. It also clarifies these are completed transactions, not listings. It does not name the obvious sibling alternative card_price_history, so the differentiation is implicit through 'most recent' and 'up to 10'.

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 implies its use case ('most recent verified sales for one card') and points to where card_id comes from via the schema ('search_card / slang_lookup'). However, it never says when to prefer this over card_price, card_price_history, or market_movers, and gives no exclusions or alternatives. Usage must be inferred.

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