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

Annotations already indicate readOnlyHint and idempotentHint, and the description adds no contradictory behavioral traits. It includes category meanings, but these are also present in the schema. No extra context like pagination, data freshness, or limitations is provided.

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 purpose sentence is front-loaded and the Args list is compact and readable. However, it duplicates some information already in the schema, making it slightly redundant though still efficient.

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 read-only tool with three parameters and no output schema, the description covers all parameter meanings and the types of movers returned. It could mention the return format (e.g., a list of tickers) but remains adequate for understanding the tool's capabilities.

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 67%, and the description largely repeats the same numeric codes for category and country. It adds minimal semantics for 'num' as 'Number of results,' which is somewhat self-evident, so it does not significantly enhance the schema.

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 clearly states it returns today's market movers with specific categories (gainers, losers, most active), using the verb 'Returns' and a specific resource. It is distinguishable from siblings like get_market_performance, though it does not explicitly mention alternatives.

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?

No guidance on when to use this tool versus similar market data tools, nor any exclusions or alternative tool names. The description only explains what it returns, not when it should be selected.

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