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

Annotations already declare readOnly, idempotent and openWorld, so the safety profile is covered. The description adds genuinely new behavioral context: the paid x402 flow, the price, and the two-phase invocation where omitting payment_signature returns payment requirements rather than data. It does not cover error handling or rate limits, so it is strong but not exhaustive.

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?

Three front-loaded sentences plus a sample pointer; the purpose and when-to-use lead, and the payment mechanics follow. The price is restated from the title, which is minor redundancy rather than bloat.

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 no output schema, the description still covers the payment-gated return path and points to a sample response, which is the key unknown for this tool. The shape of the actual indicator payload (per-country, per-year values) is only implied via the sample link, leaving a small gap.

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 the schema already documents years, countries, indicators and payment_signature, including defaults and the omit-to-get-requirements behavior. The description restates the payment_signature consequence but adds no format or constraint detail beyond the schema, so baseline 3 applies.

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 and resource ('Get official macro figures for a country') and names the concrete use cases (research, market sizing, country-risk). No sibling tool covers macro/economic indicators, so it is trivially distinguished from the rest of the catalog.

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 gives an explicit selection condition: 'Use when a figure must be citable to an official source,' which tells the agent when this beats ad-hoc or unofficial sources. It stops short of naming exclusions or alternative tools, but no obvious sibling competes for the same intent.

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