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

Annotations already declare readOnly, idempotent, non-destructive, so safety is covered; the description adds real context beyond that: cost of 1 credit, availability on every plan, and the plan-tier ceiling on hours_ahead. It doesn't mention rate limits or result-size behavior, 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 tight sentences: the first front-loads the resource and payload, the second gives the routing reason plus cost. Zero filler, no repetition of the title.

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 discovery tool with a full schema and an output schema, the description covers purpose, cost, plan gating and the intended workflow role. It leaves minor gaps only, such as typical result volume or whether scratchings are inline per runner, which a caller might want before spending a credit.

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 all four parameters (date, country, categories, hours_ahead) are already fully documented including default, patterns and plan ceilings. The description adds no parameter meaning beyond the schema, making the baseline of 3 correct.

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/resource (upcoming races) and enumerates exactly what the response carries: race_id, venue, race number, start time, distance, track condition, status, runners and scratchings. The 'without prices' qualifier immediately separates it from odds/pricing siblings like race_odds and best_odds.

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?

Explicitly frames the tool as 'the cheapest way to find race_ids for the other tools', which tells the agent to use it as the discovery step before pricing/form calls. It does not name a specific alternative or state when-not to use it (e.g. when prices are needed, use race_odds), so it stops 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.