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

Annotations already declare readOnlyHint, destructiveHint=false and openWorldHint, so safety is covered. The description adds non-obvious behavior: volume_min defaults to 10 and specifically exists to filter illiquid contracts, and results are ranked by % change and carry OHLCV data. That is meaningful context beyond the annotations.

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?

The core purpose is front-loaded in one sentence, followed by a tight Args/Returns block with no filler. Structure is functional and scannable, though the docstring formatting is slightly verbose for a 4-parameter tool.

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?

There is no output schema, so the description correctly notes the return shape (list ranked by % change with OHLCV data). Combined with full parameter coverage and clear annotations, an agent has what it needs to call this tool correctly; only cross-tool routing is missing.

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 0%, so the description carries the full burden, and it documents all four parameters. Critically it supplies the allowed values (gainers|losers, us|global) that the schema lacks, plus the meaning of the volume_min default; only minor format details are absent.

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 first sentence states a specific resource and scope: futures contracts with the biggest percentage moves today. The 'futures' qualifier separates it from stock-oriented siblings like top_gainers/top_losers, though it never names an alternative explicitly.

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 when-to-use or when-not-to-use guidance, and no routing to siblings such as futures_market_overview, futures_category_snapshot, or futures_watchlist. The parameter list implies a screener use case but the description never states the conditions that select this tool.

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