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

The description adds substantial context beyond the read-only annotations: it discloses that the endpoint is a free preview, auto-selects the session, returns only the top 10 under default filters, and clarifies that hasNews is a boolean without headline text or links. It also explains that rvol is a derived premarket metric and warns that it differs from regular-session relative volume, which is valuable behavioral detail.

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 front-loaded with the core purpose and filter criteria, and the key limitations are stated early. It is somewhat long and repeats the default filter thresholds across two paragraphs, but most of the additional detail earns its place by clarifying session behavior, field meanings, and ranking logic.

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 absence of an output schema, the description compensates by enumerating the returned fields and explaining their meanings, including changePct, rvol, premarketVolume, and hasNews. It also describes ranking order and the echoed session field, so an agent has enough information to interpret results without a formal output 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?

This tool has zero parameters, so there are no parameter semantics to document. The baseline score of 4 is appropriate because the description does not need to compensate for any schema gaps.

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 scanner and scope: a low-float momentum gap scan returning top premarket or after-hours gappers. It clearly distinguishes this from the sibling macro tools by focusing on individual small-cap gappers with explicit filtering criteria, and it explains the auto-session behavior.

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 clearly states when the endpoint applies (pre-market 04:00-09:30 ET vs after-hours 16:00-20:00 ET) and what default filters are used, which gives an agent enough context to invoke it correctly. It does not explicitly compare against a named alternative tool, but the sibling tools are macro-level and clearly different in scope.

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