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

Annotations already declare readOnly, idempotent, closed-world, non-destructive behavior, so safety is fully covered. The description adds the one genuinely missing piece with no output schema present: the shape of the returned data (total, PSA 10, PSA 9 broken out by date), which tells the agent what to expect back.

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?

One short sentence, front-loaded with the resource and scope, with the returned fields in parentheses. There is no filler and nothing that could be cut without losing information.

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 simple single-parameter read tool with rich annotations and a fully described schema, the definition covers purpose and return contents adequately. The only gap is the lack of explicit routing guidance versus get_population and get_price_history, which matters given several overlapping history/population siblings.

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?

The single 'card' parameter is fully documented in the schema (PokeInvest ID, numeric URL ID, or name with best-match resolution), so the description has nothing to add. It does not mention identifier flexibility or the best-match fallback, but with 100% schema coverage the baseline of 3 applies.

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 names a specific resource (PSA population history for a card) and enumerates the returned series (total, PSA 10, PSA 9 by date). The phrase 'over time ... by date' implicitly separates it from the snapshot-oriented get_population sibling, but it never names that sibling explicitly.

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?

Usage is only implied: 'over time' suggests historical trend questions versus a current snapshot, which is enough for an agent to route correctly against get_population. There is no explicit when-to-use/when-not statement, no mention of date ranges or granularity limits, and no stated alternative.

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