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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely non-obvious context: the default year resolution and sort direction, aggregate exclusion, and especially the paid x402/$0.02 USDC cost on Base, which the agent must know before invoking.

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 core behavior is front-loaded in a single dense sentence, followed by a compact licensing/cost line. Nearly every clause carries information; the 'CC BY 4.0' clause is the only marginal element.

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 ranking tool with full schema coverage and no output schema, the description covers defaults, filtering, aggregate handling, and payment. Return shape and pagination behavior are left implicit, a minor gap given the parameters already imply limits.

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 all seven parameters are already documented, and the description largely restates those defaults (latest year, desc, aggregates excluded). It adds the interpretation of 'order' as highest/lowest first and confirms filter targeting, but does not go beyond the schema in any material way.

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 gives a concrete verb and resource ('Country ranking: sort all economies by one World Development Indicator for a year') and specifies scope (all economies, one indicator, one year). It is clearly distinguishable from the sibling macro_indicator (indicator lookup) and macro_country (single-country profile).

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 states the default behavior (each country's latest value, descending order) and when aggregates appear ('excluded unless requested'), plus optional region/income filtering. It stops short of explicitly naming alternatives for the single-country or indicator-lookup cases, which is the only gap.

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