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

Annotations already cover readOnly, idempotent, and non-destructive behavior. The description adds valuable context: it is 'Descriptive market state, never a prediction', includes volume so thin-volume moves are visible, and scopes to the streamed top-~300 board. No contradiction with 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 description is densely functional and front-loads the core definition, then provides routing and caveats. The final two clauses ('Descriptive market state, never a prediction. Descriptive market data only.') are slightly redundant, but overall the length is justified by the amount of guidance.

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?

Given the presence of an output schema, full parameter documentation, and annotations, the description covers all critical aspects: scope, content, use cases, alternatives, and non-predictive nature. Nothing essential is missing for an agent to select and invoke it correctly.

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% and both parameters (only, limit) are fully described there, including enum values, defaults, and cap. The description does not add meaning beyond the schema, so the baseline score of 3 is appropriate.

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 a specific resource ('biggest 24h gainers and losers across the streamed top-~300 board') and a concrete purpose (momentum discovery). It clearly distinguishes itself from siblings by naming market_brief, market_screener, and whale_radar for other use cases.

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 explicit 'Use this for' scenarios with example queries, and explicitly states which alternative tool to use for WHY, cross-filtering, and whale flow. This leaves little ambiguity about when to select this tool.

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