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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely useful behavior beyond that: it returns ids and odds, and a player with no listed props yields an empty events list rather than an error — a detail an agent cannot infer from structured fields.

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 what is returned, followed by usage and prerequisites. No filler; every clause carries either a return-shape, a use case, or a hard constraint.

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 present, the description needn't detail return values, yet it still flags the key fields and the empty-result edge case. Combined with annotations and a fully documented two-parameter schema, an agent has everything needed to call it correctly.

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 both parameters documented (including the slug example and both allowed leagues), so the schema already does the work. The description only restates the league constraint and reinforces the slug source, adding marginal meaning beyond the schema — 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?

The description states a specific verb and resource — getting a FanDuel Sportsbook player's prop markets for upcoming games — and names the returned artifacts (event, market and selection ids plus current odds). That scope naturally separates it from team-level and stats tools, though no sibling (e.g. fanduel_sportsbook_market_prices or fanduel_sportsbook_team_odds) is named as the alternative.

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?

"Use it to price a player's lines" gives an explicit use case, and prerequisites are spelled out: league must be nfl or nba and the player must be a slug from fanduel_sportsbook_players. There is no statement of when NOT to use it or which sibling to prefer for team/event-level pricing.

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