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

Annotations already cover readOnly and idempotent, so the description's added value is scope information: it is cross-market rather than single-symbol, and sector/min_market_cap apply only to equities. Nothing contradicts the annotations, though it says nothing about response ordering or how ties/empty universes are handled.

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 dense sentences, zero filler, with the capability statement front-loaded and the disambiguation trailing. Every clause earns its place.

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 screener with no output schema and no required parameters, the description adequately tells the agent what comes back and how to scope the call. It could still be more explicit about the default metric grouping and row limits, but that information lives in the schema.

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 all five parameters are already documented in the schema; baseline 3 applies. The description only reiterates that the sector and market-cap filters are equity-scoped, adding little beyond the schema's own wording.

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 (cross-market discovery screener) plus the exact contents of each output list (gainers, losers, volume leaders, high-IV underlyings). It also names the sibling it is not (get_options_chain), so an agent can distinguish it without opening either 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?

"Use to discover candidate tickers across the market" gives the affirmative case, and the follow-up clause names the alternative tool and the condition that selects it (inspecting a specific symbol's option chain). This is the same when/when-instead structure as the high-scoring calibration example.

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