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

Annotations only declare readOnlyHint and openWorldHint; the description adds that the result depends on Yahoo serving a particular HTML table, warning the agent that output may be conditionally unavailable. That extraction-fragility caveat is real value beyond the annotations, though permissions and rate-limit behavior are unaddressed.

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, zero padding, with the core action and the availability constraint front-loaded ahead of the alternative-tool pointer. Every clause 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?

An output schema exists, so return values need not be described, and the single parameter plus safety annotations are covered. The only residual gap is which valuation fields are returned and how the HTML-dependency failure surfaces, which is minor for this tool's complexity.

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% with a single, well-documented symbol parameter, so the schema already carries the semantics. The description adds no format or symbol-convention detail beyond it, making the baseline 3 appropriate.

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?

It states a specific verb ('Fetch'), a specific resource ('the valuation table from one Yahoo Finance key-statistics page'), and scopes it to a single page. It also names the sibling yahoo_finance_ticker_info, so an agent can tell the two apart without opening either 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?

It routes the agent explicitly to yahoo_finance_ticker_info for the broader company-statistics record, which is a concrete alternative. It lacks a clear statement of when valuation specifically is preferred over related siblings like yahoo_finance_ticker_financials, so it stops short of a full when/when-not rule.

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