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

Annotations already supply readOnlyHint and openWorldHint, so safety is covered. The description adds genuinely new behavioral context: the scope is restricted to today's races and the result set is large (~500 across all tracks), which matters for pagination strategy. It still omits whether the list is limited to races open for betting or rate/pagination limits, so not 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?

Two dense sentences, front-loaded with what the tool returns, then how to filter/sort/page. The field enumeration is somewhat redundant given an output schema exists, but it is compact and no sentence is 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?

With an output schema, full parameter documentation and annotations all present, the description only needs to convey scope, scale and query axes — and it does. The one gap is that it never clarifies the relationship to the sibling search/filters tools, so an agent could still pick the wrong entry point.

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%, so every one of the 11 parameters is already documented in the schema. The description paraphrases the main filter axes and sort/paging options but adds no syntax, defaults, or edge-case detail beyond what the schema states, so the baseline 3 applies.

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 ('List today's FanDuel Racing races across all tracks') plus result volume (~500) and returned fields, so the agent knows exactly what it gets back. It does not, however, distinguish itself from close siblings such as fanduel_racing_search or fanduel_racing_past_races, leaving the agent to infer that this is the today-only listing vs. historical or keyword search.

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 second sentence describes the intended use ('find races by country, race type, status or the next N minutes') and mentions sorting/paging, which implies when to reach for it. But it gives no explicit when-not guidance or alternative routing against fanduel_racing_search, fanduel_racing_filters or fanduel_racing_past_races, so usage is only implied.

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