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

Annotations already declare readOnlyHint/idempotentHint/non-destructive, and the description adds real value on top: the 30-minute data refresh cadence and the full list of returned metrics (since there is no output schema). It does not mention auth, plan limits, or default behavior with zero filters.

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?

Front-loaded with the core purpose, then the return fields, then the compare behavior, then refresh cadence. The stat enumeration is dense but earns its place given there is no output schema; only the field list borders on over-listing.

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 tool with no output schema and fully documented params, the description covers purpose, return shape, compare mode, and freshness. It leaves the default result set when no filter is supplied unstated, which is a minor gap for a 0-required-param tool.

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 meaningfully extends the compare parameter beyond its schema text by explaining that it ranks players head to head and reports the chance each scores more. It adds no similar depth for limit or team.

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+resource (season-long fantasy start/sit for the current NFL week) and enumerates the projection fields returned, so an agent knows exactly what it gets. It does not name or differentiate itself from close siblings like invoke_nfl_projections, so it falls short of a 5.

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 gives one explicit usage rule (pass compare with 2+ names to rank head to head), which is genuinely useful. But it never says when to prefer this over invoke_nfl_projections or invoke_nfl_player_pool, and there are no exclusions or prerequisites.

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