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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered; the description adds genuine context beyond that by enumerating returned content (all stored dates, next edition registration state and check timestamp, Boston-qualifier status) and explaining that go-links are stable redirects whose destination is named by official_url. It doesn't cover behavior on an unknown slug, which keeps it below a 5.

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?

A single front-loaded sentence that names the key, then the payload, then the link semantics — every clause carries information and nothing is repeated from the schema.

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 carries the return-value burden and does so thoroughly, including link behavior. The only missing piece for a single-parameter lookup is error handling for an invalid or unknown slug.

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 100% with an inline example, so baseline is 3; the description adds provenance that the schema lacks, telling the agent the slug must come from search_races rather than be guessed.

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 ('One race by its Marathon Scout slug') and immediately ties it to the sibling that produces the slug (search_races), so an agent can tell it apart from the search tool 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?

Implies the correct workflow by noting the slug comes 'from search_races' and that live-tracking links exist 'once confirmed', which sets expectations. It never states an explicit when-not-to-use or an alternative for fetching multiple races, keeping it short of a 5.

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