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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds real behavioral value beyond that: with no league ID it degrades to a league-picker listing, and it previews the returned content (standings, gap, captains, differentials) despite there being no output schema.

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 clauses, front-loaded with the primary use case, followed immediately by the fallback behavior. No filler, no repetition of the title, and every element earns 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?

For a read-only, two-optional-parameter tool with a fully documented schema and no output schema, the description covers purpose, usage and the zero-argument path. The only gap is that it never clarifies its boundary against get_mini_league_odds, which an agent choosing between the two would need.

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% and both parameters are documented there, including that they accept either IDs or full FPL links and can be left empty. The description's mention of omitting the league ID largely restates the schema's own "Leave empty to list the manager's leagues," so it adds little beyond the baseline.

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 names the resource (FPL mini-league) and enumerates what it returns: standings, gap to the leader, rivals' captains and differential picks. That is far more specific than a restatement of the name. It does not, however, distinguish itself from the sibling get_mini_league_odds, which plausibly covers adjacent mini-league data.

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?

It states the use case explicitly ("Use this for an FPL mini-league or a manager's rivals in it") and explains the no-argument fallback (listing the manager's leagues to choose from). There is no explicit when-not guidance and no alternative tool is named for the odds/rivals overlap.

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