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

Annotations cover readOnlyHint and openWorldHint, so safety is already handled. The description still adds useful behavioral context beyond them: the data is credential-free public JSON, and the league key must be valid for the chosen sport. It stops short of noting what happens on invalid sport/league combinations or any rate limits.

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?

Front-loads the return payload, then parameters, then the sibling pointer. The long inline enum lists are somewhat bulky but are load-bearing for a parameter with no schema enum, so little is wasted.

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 need not describe return values, and all three params are documented at 100% coverage with annotations covering safety. It is complete enough for correct invocation; only edge-case behavior (invalid league/sport pair) is unaddressed.

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 the baseline is 3, but the description goes further by listing the full league enum (including international soccer codes absent from the schema's 'e.g.' list) and stating the cross-parameter dependency that league must be valid for sport. That is real semantic value beyond the schema.

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 ('Returns one athlete's bio/overview') and enumerates the exact fields returned (name, position, jersey, physicals, current team), so an agent knows precisely what it gets. It also points at espn_team_roster, separating the single-athlete lookup from the team-level tool.

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 names a related sibling (espn_team_roster) and states a validation constraint ('league must be valid for the chosen sport'), which implies correct usage. However, it never says when to use this tool instead of espn_team or espn_teams, so guidance is implied rather than explicit.

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