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 and the network dependence are structured data, not description-specific value. The description adds that data is scraped from a player page, which hints at upstream availability risk, but says nothing about behavior when the id is invalid or the player is missing. Adequate but thin for a tool that annotates itself as open-world.

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, no filler. The capability statement is front-loaded and the second sentence is pure routing guidance, so nothing is wasted and nothing important is buried.

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?

An output schema exists, so return-value detail is unnecessary, and the description still summarizes the payload (bio + current-season statistics). Both required params are fully documented in schema and corroborated by the description. The only real omission is any fallback path when a player id is unknown, which is where yahoo_sports_player_search would belong.

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%: 'league' is documented as a Yahoo league key from yahoo-sports-leagues and 'player' as a numeric id from a roster response's player url, including an example (42019). The description adds only the singular scope ('one player') and confirms roster-based id sourcing. Baseline 3 applies since the schema already carries the parameter semantics.

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?

A specific verb ('Fetch') bound to a specific resource ('one Yahoo Sports player's bio and current-season statistics'), plus the source ('player page'), which tells an agent exactly what comes back. It differentiates itself from team-level siblings by naming them as prerequisite lookups. It does not, however, distinguish itself from the close sibling yahoo_sports_player_search, which is the obvious competing choice.

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?

Gives a concrete workflow: obtain the player id via yahoo_sports_team or yahoo_sports_team_roster first, which tells the agent this is a detail/lookup tool, not a discovery tool. It stops short of naming yahoo_sports_player_search as the alternative when only a name is known, and gives no when-not-to-use condition.

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