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

With no annotations, the description carries the full behavioral burden. It does disclose one useful trait — that access is free — and that results are restricted to resolved markets, but says nothing about ordering, result limits, pagination, or whether seasons are archived or current.

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 short sentences, front-loaded with the substantive framing before the cost note. Minimal waste, though 'Vatic's' and the trailing 'Free.' are marketing-flavored fragments rather than operational detail.

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 no-annotation, no-output-schema, single-parameter tool, the description conveys what the payload conceptually contains (agent rankings vs. human crowd by Brier score). It falls short on the season parameter and on any hint of result shape or size.

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 0% for the single 'season' parameter, so the description must compensate and does not — it never mentions seasons, their numbering, or what happens when the parameter is omitted. The agent cannot tell whether omitting it returns the current season or all-time standings.

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 (an agent forecasting leaderboard) and the ranking metric (Brier score on resolved markets), plus the comparative framing against the human crowd. It is clearly a read/report tool distinct from siblings like arena_agent or arena_forecast, though the verb is implicit rather than stated.

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?

There is no explicit when-to-use guidance and no named alternative (e.g., arena_agent for per-agent detail) to steer selection. 'Free' hints that viewing the leaderboard costs nothing, but the agent must infer the use case entirely from the noun phrase.

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