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

Annotations declare readOnlyHint=false, which would otherwise puzzle an agent given the "Read" framing; the description resolves this by disclosing the precise conditional mutation (completing a previously committed draw) and its limits (never substitutes a winner, which aligns with destructiveHint=false and idempotentHint=true). Return payload is also stated: original winners and share image.

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 short sentences, zero filler, and the core action plus lookup key come first while the conditional side effect follows. Every sentence carries distinct information.

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 compensates by naming the return contents (original winners, share image), and it explains the side effect an annotation-only view would hide. Only error/not-found behavior for an invalid or unknown slug is unaddressed.

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 0%, so the single parameter depends on the description, which does supply the important qualifier "public slug" — distinguishing it from an internal draw ID. It does not restate the 10-character pattern, but that is reasonably left to the schema's regex constraint.

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 pair and resource ("Read and verify a Winner Picker result") plus the lookup key (public slug). The closing clause "never picks a replacement winner" explicitly separates it from the sibling draw_winners tool, so an agent can route between them without opening either 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?

The conditional "If randomness is now available, completes the previously committed draw" tells the agent when this call is meaningful — after a draw has been committed but randomness wasn't available. It does not name draw_winners as the alternative for creating a draw, relying on implication rather than an explicit when-not.

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