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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description adds genuinely non-obvious behavior: prize amounts are omitted for powerball/megamillions because they depend on state and multiplier, and the response is only a drawstoday.com link carrying no result itself. That last disclosure is the kind of return-shape warning an agent needs, though failure modes (invalid numbers, unsupported draws) go unmentioned.

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 sentences, front-loaded with the core action, and each sentence carries distinct information (default draw, per-game return differences, response is a link). The middle sentence is dense with clauses but nothing is 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 correctly takes on the burden of explaining what comes back (a link, not a result) and why prize values are absent for two of three games. What's missing is error/failure behavior and any hint about the link's expiry or stability, minor for a read-only lookup tool.

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 75% and already documents the numbers/extra_number ranges and per-game applicability, so the description need only fill gaps. It does so by explaining that 'draw' defaults to the latest draw, which the schema leaves to a get_draw cross-reference, and by naming the games that ignore extra_number.

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 ('compare your numbers with a draw') and enumerates what each game variant returns (rank/prize for kr645, match only for powerball/megamillions). It doesn't differentiate itself from siblings like get_draw or pick_numbers, but the operation is unambiguous.

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 implied rather than stated: the description notes the draw defaults to the latest 'unless you give one', which tells the agent it can be omitted, and points at get_draw for draw formatting. There is no explicit statement of when to prefer this over get_draw or the other siblings.

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