One draw

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

Annotations already mark it read-only, idempotent, and open-world, but the description adds substantial behavioral context: official API source, publication times, the possibility of a missing prize table, the meaning of prizes_pending, and the warning never to fill in unavailable numbers. This is exactly the kind of context annotations cannot provide.

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 description is front-loaded with the core lookup behavior and then adds important caveats in a logical order. It is long, but most sentences carry operational value; the parenthetical Chinese ad disclosure and final link note are useful but make the text slightly dense.

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 still explains that results match latest_draw's fields and includes a `more` link field. It covers timing, missing data, pending prizes, error behavior, and official-source caveats, which is sufficient for an agent to invoke this tool correctly.

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?

Even though schema coverage is 100%, the description adds meaning beyond the schema: dates are Taiwan time, period is required for bingo due to multiple daily draws, and a date alone can be ambiguous. It also explains that missing draws produce an error listing the game's draw days.

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 states a specific verb and resource: retrieving one official draw by period number or date. It distinguishes its lookup modes and explicitly references latest_draw as the source of comparable fields, so an agent can identify it without opening the schema.

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?

It gives clear selection guidance for date versus period, including the important rule that bingo requires a period because 203 draws occur per day. It also explains the no-draw error behavior. It does not explicitly contrast itself with latest_draw or list_draws, which keeps it from a 5.

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