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

Annotations only declare readOnlyHint/openWorldHint/idempotentHint; the description goes well beyond them, disclosing that future-dated moves are excluded by default, what planned=true actually returns, and that profiles are re-read only every 30 days so the newest moves can be absent. It also states that fee_eur is often null and must never be reported as 0, which is a genuine data-interpretation rule.

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?

Dense but front-loaded: the returned fields come first, then filtering, then caveats about exclusions and data freshness. A long single block, and the parenthetical field glosses make it heavy, but almost every clause carries information an agent needs.

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 no output schema, the description fully compensates by enumerating return fields, enum-like values, and null-fee handling, plus the future-move exclusion and 30-day refresh lag. Nothing an agent needs to call or interpret this tool correctly is missing.

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 adds real semantics: direction only applies with team_id, league_id means moves in or out of that league's current teams, window is derived 'other by the date', and fee_eur nulls mean 'not known' rather than zero. That is meaningfully more than the schema text restates.

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 ('Soccer transfers from player profiles') and then enumerates the exact fields returned (player, from/to team, date, season, window, type, fee_eur). No sibling tool covers transfers, so there is no ambiguity to resolve, and an agent can tell instantly what payload to expect.

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 concrete usage context: filter by league, team, season and window; sort by fee for biggest moves. It also clarifies when the returned set shifts (planned=true yields only moves after today). It stops short of naming an alternative tool or stating when not to use this one, but for a leaf data tool the routing guidance is clear.

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