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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful context beyond that: the credit cost structure (1 credit plus 1 per include), which an agent needs for cost-aware planning. It stops short of saying how fresh the prices are or whether they are cached snapshots.

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 short sentences, front-loaded with what is returned and from where, followed by the cost. Nothing is padded or redundant.

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 no output schema, the description carries the burden of describing returns, and it does so by naming the three sources and the native-currency convention. It is nearly complete for a simple two-parameter read, with only freshness/timing of the prices left unstated.

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 the schema already documents card_id and the graded/population include values with their credit costs. The description's "1 credit, +1 per include" largely restates the schema's own cost notes, so it adds little beyond the baseline.

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 gives a specific verb and resource ("Current prices of one card") and names the three data sources (Cardmarket, US market, eBay sales) plus their native-currency treatment. This clearly separates it from get_price_history (historical) and compare_prices, though it never names those siblings 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: an agent can infer this is the single-card current-price lookup, and the per-include credit note signals optional add-ons. There is no explicit when-to-use or when-not-to-use versus get_price_history, compare_prices, or price_summary, all of which sit near this tool.

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