Market movers

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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds real behavioral context beyond that: only Egypt and US actually return data despite the enum's uae/simulator values, and US lists may contain instruments flagged tradable: false — a caveat an agent needs before acting on results.

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 short sentences with no filler; the core purpose leads, and the scope caveats (Egypt/US only, tradable: false) follow. Every clause carries information an 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?

With no output schema, the description usefully characterizes the return shape (instruments ranked by return with price and today's change) and the tradable flag. It stops short of clarifying whether type=both yields two separate lists or how the limit interacts with that, which is a minor remaining gap for a 4-parameter read tool.

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%, so the baseline is 3 and the schema already documents all four parameters and their enums. The description still adds value by confirming the ranking periods, restating the Egypt/US restriction that constrains the market enum, and describing what each returned instrument carries (price and today's change).

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 (Thndr's top gainers/losers), the ranking basis (return), the supported periods, and the geographic scope. An agent can tell this apart from neighbors like screen_market, get_trending, or get_price_performance without opening any 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?

Usage is only implied: this is the tool for ranked top-mover lists, and the type/period parameters hint at how to narrow it. There is no explicit statement of when to prefer this over screen_market or get_trending, and no exclusions or prerequisites are given.

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