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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds real behavioral context beyond that: pricing (0.001 credits per call) and unauthenticated rate limits (25 calls/day per address), which an agent needs to plan calls.

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?

One tight sentence carries the core definition and return shape, with pricing/auth metadata front-loaded in a parenthetical. No filler, though the param behavior is absent rather than omitted for brevity.

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?

With readOnly/openWorld annotations and no output schema, the description sufficiently conveys what the tool returns, its cost model, and its access requirements. The only meaningful hole is the undocumented history_years parameter.

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 0% and the single parameter history_years (default 5, max 50) is never mentioned in the description. The description does not compensate for the gap by explaining the lookback window's effect on percentiles or zones.

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 exactly what the tool computes (US corporate equities ÷ GDP) and what it returns (zones and historical percentile), which is a specific verb+resource. It clearly differs in substance from the sibling indicators_shiller_pe, though it never names that sibling to make the routing explicit.

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 when-to-use or when-not guidance is given, and the closely related sibling indicators_shiller_pe is not mentioned. Usage is only implied by the general nature of a valuation indicator.

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