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 the field inventory of the response, which is genuinely useful behavioral context, but says nothing about error behavior for unknown ids or whether the id must be a live/active player. With an output schema present, the field list is somewhat redundant.

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?

Three short sentences, front-loaded with what is returned and ending with the alternative-tool pointer. It is efficient, though the 'id: Required. Numeric MLB player id' clause duplicates the schema verbatim rather than earning its place.

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 annotations covering safety, a full output schema covering return values, and 100% schema description coverage on the single parameter, the description only needs to state scope and routing. It does both, so nothing essential is missing, though it could note the id format or error case for full completeness.

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% for the single required id parameter, so the schema already documents it as a required numeric MLB player id. The description only restates 'id: Required. Numeric MLB player id,' adding no syntax, range, or sourcing guidance 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?

States a specific verb (Returns) and resource (an MLB player) and enumerates the exact fields returned: identity, biographical information, position, handedness, active status, current team. It also names the sibling it is not (mlb_player_stats), so an agent can distinguish it from the stats tool without opening either schema.

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 routes the agent to mlb_player_stats 'to get MLB player season statistics,' which clarifies when this tool is the wrong choice. However, it never states the positive trigger (lookup of a single player by id) or mentions related alternatives like mlb_statcast_player_details or flashscore_player.

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