get_market_movers

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

Annotations already declare the operation read-only, idempotent, non-destructive and open-world, so safety is covered. The description adds genuinely new context beyond that: the data source (Yahoo Finance screeners), the 'today's' freshness scope, and the exact return fields (price, change %, volume, market cap). It omits rate limits or market-hours caveats, keeping it from a 5.

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?

Front-loaded with the one-line purpose, then cleanly separated Args/Returns blocks, which is a good structure for an agent. The 14-value category list is a long wall of text but the content is necessary given the schema lacks enums, so it earns its space.

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 zero-required-param, read-only screener this covers the essentials: source, freshness, valid categories, count bounds, and return shape (even though an output schema exists, so that is partly redundant). Missing only operational caveats like whether data is real-time or delayed, and how it relates to sibling market tools.

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 0% and neither parameter has an enum in the schema, so the description carries the full burden — and it does so well by enumerating all 14 valid category values and specifying the count range (1-50, default 10). It does not explain what any individual category means, so it stops short of a 5.

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 first sentence gives a specific verb and resource ('Get today's market movers') plus the data source ('Yahoo Finance screeners'), which is enough to separate it from adjacent tools like get_market_summary or get_trending_tickers. However, it never explicitly says how it differs from those siblings, so it falls short of a 5.

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?

There is no guidance on when to select this tool over the many overlapping siblings (get_trending_tickers, get_market_indices, get_sector_performance, get_market_summary). Usage is only implied by the name and category list; no conditions, prerequisites, or exclusions are stated.

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