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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds genuine behavioral context beyond that: it works without a team, ranks the user's own players when a team is known, and scope 'all' ranks the whole game. It stops short of describing output format or ranking criteria, so it is not a 5.

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 tight sentences, front-loaded with the trigger condition, then the no-team and with-team branches. No filler and every clause carries information.

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 two-optional-param, no-output-schema tool, the description covers the trigger, both input branches, and the fallback behavior, which is enough to call it correctly. Only the shape of the returned ranking is unspecified, which is a minor gap.

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 already 100%, so the baseline is 3, but the description adds meaning by tying 'scope' and 'team_id' together behaviorally (with a team it ranks their players; 'all' ranks the game) rather than merely restating field definitions.

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 ('who to captain ... in Fantasy Premier League this gameweek') and names the scenario including Triple Captain. An agent can distinguish this from siblings like get_manager_squad or rate_my_team without opening any 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 says when to call it ('when someone asks who to captain'), that it works without a team ID, and how behavior changes with a team ID or scope 'all'. Alternatives and conditions are spelled out rather than left to inference.

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