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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint. The description adds crucial behavioral details beyond these: the fallback mechanism with ok=False and the api_key requirement difference between public and /mcp/mcp endpoints. This is valuable context an agent needs to interpret responses correctly.

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 main purpose, and every sentence earns its place. No redundancy or filler; the fallback and api_key notes are essential and efficiently phrased.

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?

Since an output schema exists, the description needn't detail return values. It covers all necessary contextual information: purpose, fallback condition, and auth requirements. Nothing an agent needs to decide and invoke correctly is missing.

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 has a single optional `api_key` with no description (0% coverage). The description fully compensates by explaining when the key is required and when it is optional, providing precise semantics the schema lacks.

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 clearly states the verb 'Fetch', the resource 'today's Daily Pair', and differentiates it via 'trending matchup chosen at 00:00 UTC' and the 'vote_of_the_day' agent template. It explicitly names the sibling `aimrank_get_matchup` as an alternative, making the purpose 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?

The description gives explicit usage context: when to call (to get the daily pair) and when not to (if cron hasn't run, fall back via ok=False to `aimrank_get_matchup`). It also provides endpoint-specific api_key guidance, covering prerequisites.

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