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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the description earns credit for adding non-obvious operational context: a $0.002 USDC charge per successful call via x402 on Base/Solana/Arc, no charge on failures, and the ESPN upstream plus the note that Pro Football Reference blocks automated access. What it does not disclose is pagination behavior beyond the page param or rate limits, which keeps it below 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?

Purpose and default sort are front-loaded, which is good, but the sentence then spends a long clause enumerating every box-score column (completions, attempts, completion %, Y/A, sacks, passer rating, QBR, plus rushing, receiving, defense, scoring, returns, kicking, punting). Since an output schema exists, that enumeration largely restates what the response already conveys and bloats an otherwise compact definition.

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 an output schema present, the description need not explain return values, and it covers the remaining essentials: scope, data source, season range, pricing/auth path, and two neighboring tools. The one gap is differentiation from the closest sibling, dev_nfl_stats, which an agent choosing between them would want stated.

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 every parameter is already documented inline; the baseline is 3. The description adds only two meaningful facts beyond the schema: the default sort is passing yards and the season floor is 2004, which usefully bounds the free-form 'season' string but is not substantial extra parameter semantics.

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: an NFL player season statistics leaderboard, with the default sort (passing yards), the stat families covered, the season range (2004 to now), and the upstream data source (ESPN's public stats API). It explicitly separates itself from dev_baseball_reference and dev_football_data_couk, but does not distinguish itself from the far more confusable sibling dev_nfl_stats or dev_espn_nfl_scoreboard.

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 names two alternatives with their use cases ('when you need MLB player season statistics', 'when you need European football match results with statistics and betting'), which is real routing guidance. However, those siblings are not the ones an agent would actually confuse this with — dev_nfl_stats and dev_espn_nfl_scoreboard are left unaddressed, so the guidance is implied rather than decisive for the overlapping case.

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