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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds behavior beyond that: the default tab is 'popular', the response lists every available tab slug, and an unknown tab or ended event produces an error. It does not mention auth or rate limits, but for a read-only fetcher it provides useful operational detail.

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 main action and scope. The second sentence adds the response tab listing and error behavior without wasting words.

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?

The description covers the core fetch behavior, default tab, tab categories, response tab listing, and error cases. With a fully described input schema and an output schema, it is nearly complete; the only gap is guidance on when this overlaps with dedicated sibling tools for props or market prices.

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%, so every parameter is already documented in the input schema. The description reinforces tab semantics by naming the default and explaining that unknown tabs error, but it adds little for state, event_id, or market_type beyond what the schema already states. Baseline 3 is appropriate.

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: fetch one FanDuel Sportsbook event with markets and odds from one tab. It also clarifies the default tab and lists possible tab categories. It does not explicitly differentiate itself from sibling tools like fanduel_sportsbook_player_props or fanduel_sportsbook_market_prices, but the single-event, single-tab scope is clear.

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 implies usage by saying it fetches one event's markets for a given tab and that an unknown tab or ended event is an error. It does not state when to use this instead of sibling tools such as fanduel_sportsbook_player_props or fanduel_sportsbook_market_prices, leaving overlap ambiguous.

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