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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuine behavior beyond that: the payload contents (standings, leader gap, rivals' captains, differentials) and the branch where omitting league_id returns the manager's league list instead of standings.

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 primary use case leads, and the no-parameter fallback follows, which is exactly the order 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 carries the return-value burden and does so by listing the four things it returns. Minor gaps remain around the case where both parameters are omitted and any league-size/rank limits, but nothing essential to a correct call 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 description coverage is 100%, so the schema already documents both team_id and league_id, including link formats and the "leave empty" behavior. The description restates the empty-league_id case without adding format or precedence detail, so it only matches rather than exceeds the schema — baseline 3.

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 concrete resource (FPL mini-league standings) and enumerates the specific outputs: standings, gap to the leader, rivals' captains and differential picks. It is clear what the tool returns, but it never names the obvious sibling get_mini_league_odds, so an agent must infer the boundary itself.

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 this for an FPL mini-league or a manager's rivals in it" gives an explicit usage trigger, and the second sentence explains the fallback mode when no league ID is supplied. No exclusions or competing-tool routing are offered, which keeps it below a 5.

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