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

With no annotations, the description carries the transparency burden and does disclose the key behavioral distinction between recent-history mode and specific-date mode. It gives an accurate sense of what the operation returns, though it does not discuss output structure, error behavior, or edge cases. For a low-risk read-only tool, that is adequate but not detailed.

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?

The definition is two short sentences with no filler: the core purpose and modes are front-loaded, and the list_lotteries instruction earns its place. It is compact while still conveying the essential behavior.

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 two-parameter tool with no output schema, this description covers the essential invocation facts: what data is returned, the optional-date behavior, and where to find valid lottery codes. It does not describe the return format or explicitly differentiate from latest_results, but given the low complexity these are minor omissions.

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 schema already documents both parameters with 100% coverage, so the baseline is 3. The description adds value by specifying that 'lottery' is a code sourced from list_lotteries and clarifying that omitting 'date' yields the most recent draw. This is genuinely useful guidance beyond the schema text.

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 the resource ('Winning numbers for one lottery') and the two retrieval modes, making the tool's purpose clear. It also references list_lotteries for code sourcing, which helps separate it from the listing sibling. It stops short of explicitly contrasting itself with latest_results, so it is not a full 5.

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 establishes clear context: use this when you need winning numbers for a single lottery, either as recent history or for a specific past date. The instruction to pull codes from list_lotteries guides preparation, but there is no explicit guidance on when to prefer latest_results instead. Usage conditions are implied rather than spelled out.

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