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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety and open-world behavior are covered. The description adds the default limit value of 18, which is useful, but does not go further into ordering, freshness, or rate-limit behavior.

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?

Two sentences, front-loaded with the core purpose, followed by the default and use case. No filler or repetition.

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 simple single-parameter list tool with annotations, an output schema, and full schema coverage, the definition covers what is needed: scope, returned fields, default, and use context. The only missing piece is distinguishing it from the similar markets/movers siblings.

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% and there is only one optional parameter, so the baseline is 3. The description improves on this by disclosing the default value (18), which the schema itself does not state, adding real semantic value.

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?

States a specific verb ('List') and resource ('instruments currently trending on Google Finance') plus the returned fields (ticker, exchange, name). It does not, however, differentiate itself from near-identical siblings such as google_finance_markets_movers or google_finance_markets_top, so an agent must infer which trending/list tool applies.

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?

'Use this for a market-wide snapshot' gives an implied use context, but with siblings like google_finance_markets_top and google_finance_markets_movers present, no explicit when-not or alternative routing is provided. Usage is inferable but not disambiguated.

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