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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=false), yet the description adds substantive behavioral context: the ranking methodology for each mode, the output cardinality cap (up to 8 up and 8 down), and the meaning of the base_effect row flag. That is real disclosure beyond the structured fields.

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?

Three dense sentences with the headline purpose front-loaded, followed by the two mode definitions and the output/edge-case notes. No filler; every clause conveys information the agent needs.

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 single optional enum parameter with no output schema, the description is nearly complete: it explains both modes, the row count limits, and the base_effect caveat. The only missing piece is what happens when kind is not supplied.

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%, so the description must carry the enum semantics, and it does: it defines kind=movers as a 30-day revenue-change vs price-change divergence rank and kind=momentum as a 14-day composite of revenue, net-flow yield and health changes. It omits the default behavior when kind is omitted (the parameter is not required), a minor gap.

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 states a specific resource ('Biggest movers') and then precisely defines the two ranked views the tool produces, so an agent knows exactly what it returns. It does not name or contrast any sibling tool, which keeps it just short of a 5, but the purpose is unambiguous.

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 explains what each kind value means and when each ranking is appropriate (30-day revenue vs price divergence for movers, 14-day composite for momentum), which is useful selection guidance for the one parameter. However, it gives no guidance on when to call this tool versus siblings like tc_screen, tc_compare or tc_series, and no prerequisites.

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