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

Annotations already establish read-only, idempotent, non-destructive behavior, so the bar is lower. The description adds genuinely new context: the freshness guarantee ('newest'), the full operator coverage including Perdana's afternoon draw, and a negative scope declaration that results are official only with no forecasts. It stops short of stating staleness or caching behavior.

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 sentences, front-loaded with the core action and scope, followed by a brief boundary clause. The operator enumeration is long but earns its place by defining exactly what 'every operator' covers.

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 no-parameter, no-output-schema read tool, the description covers what is returned (latest official draw per operator), who is covered, and what is out of scope. An agent has everything needed to select and call it 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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The enumerated operator list is scope information rather than parameter semantics and is not misrepresented as input.

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 ('Returns the official newest 4D draw result') and scopes it precisely to 'every operator,' enumerating all ten operators plus Perdana's afternoon draw. The 'every operator' framing implicitly separates it from the sibling get_operator_results, 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 implied by 'newest ... for every operator' versus siblings like get_results_by_date and get_operator_results, and the closing clause 'Official results only; no number recommendations or forecasts' usefully rules out a class of misuse. However, no alternative is named and no condition for choosing this over get_results_by_date is given.

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