screen_etf

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

Annotations already declare readOnlyHint=true and idempotentHint=true, covering safety expectations. The description adds only that the tool returns ETFs matching filters, which is basic behavior. No additional behavioral traits (e.g., pagination, rate limits, data ties) are disclosed, but with this tool's simple read-only nature, a 3 is appropriate.

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 two concise sentences that immediately state the tool's purpose and return behavior. No filler or redundant details; it earns its place.

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 screening tool with a fully documented input schema and an output schema present, the description is complete enough. It conveys the core purpose and result, while the schema covers parameter details and the output schema covers return structure.

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 100%, so the input schema already documents all parameter meanings and valid values. The description's phrase 'performance and technical criteria' provides a high-level hint but doesn't add details beyond the schema, so the baseline 3 applies.

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 the tool screens ETFs based on performance and technical criteria and returns matching ETFs. The verb 'Screen' and specific resource 'ETFs' make its purpose unambiguous, and it is naturally distinguished from sibling tools like screen_stocks and screen_forex by the asset class.

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?

The description clearly identifies the context: use when screening ETFs. No explicit when-not or alternative tool references are given, but the ETF-specific scope makes usage obvious. It lacks direct mentions of when to prefer other screen_* tools, so it doesn't reach a 5.

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