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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false, so the description only needs to add context beyond safety. It adds ordering behavior ('newest first'), the inclusion of tune-ups, the returned fields, and the secondary fastest-result summary.

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 scope and ordering, followed by concrete output fields and the additional fastest-results behavior. Every clause adds useful information and there is no filler.

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 read-only list tool with an output schema and strong annotations, the description is nearly complete. The only mild gap is that it does not clarify how the distance filter interacts with the 'fastest result at 5K, 10K, half marathon and marathon' summary, which could be ambiguous when a distance filter is applied.

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 description coverage is 100%: limit has a clear 'Most rows to return' description and distance has 'Only races at this distance.' The tool description adds no additional semantics for these parameters, which is acceptable given the schema already carries the burden.

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: 'Every race... in the history, newest first, tune-ups included', and enumerates the returned fields. This clearly separates it from sibling list tools like list_runs or list_courses.

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 clear context for when to use this tool: when an agent needs race history, including tune-ups, with fastest-result summaries. It does not explicitly name alternative sibling tools or exclusions, but the scope is clear enough.

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