key_stats

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

No annotations are provided, so the description carries the burden. It discloses that missing figures come back null, which is useful. However, it does not mention whether the data is delayed, whether it requires a valid symbol, or whether it returns a single object vs. a list. The null disclosure is a positive but not comprehensive behavioral disclosure.

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 a single, information-dense sentence that front-loads the tool's purpose and then lists the metrics. It is efficient and every clause earns its place. Slightly long due to the metric enumeration, but that enumeration is valuable for an agent deciding whether this tool fits.

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 single-parameter read tool with no output schema, the description is nearly complete. It tells the agent what data comes back and the null behavior. It lacks only minor context like data source caveats or whether the symbol must be resolved first, but those are not critical for correct invocation.

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 0%, so the description must compensate. It does not explicitly define the 'symbol' parameter format, but the tool name and description make it clear that symbol is a ticker. The description adds substantial meaning by listing the returned metrics, which helps the agent understand what the symbol parameter is used for. A 4 is appropriate because the single parameter is self-evident and the description enriches its purpose.

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 states a specific verb ('Valuation and trading statistics') and resource ('for one symbol'), and enumerates the exact fields returned. It clearly distinguishes from siblings like quote (which is a lighter snapshot) and company_profile (which is descriptive rather than statistical).

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 implies usage: call it when you need valuation/trading statistics for a single symbol. It does not explicitly state when not to use it or name alternatives such as quote or compare_metrics, but the field list makes the intended use case reasonably clear.

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