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

Annotations only cover the safety profile (readOnly/idempotent/openWorld); the description adds the material facts an agent actually needs: it is paid ($0.01), how auth works (pass api_key, card at /pricing, or x402 flow explained in the response), and that binding get_changes/register_alert prevents a later gazette from silently retiring a value. That is substantial disclosure beyond structured fields.

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?

Front-loads the critical fact (PAID $0.01) and packs high information density per sentence. The parenthetical pricing fragments ('Register: $0 · Delivery after trial: $0.05') and the '...' enumeration are slightly noisy, but nothing is filler.

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?

Output schema exists so return shape need not be described, and the description still covers cost, auth, error path, alternatives and recommended follow-up calls. Against a 2-param idempotent read tool, an agent has everything needed to invoke and chain it correctly.

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 100% and country is enum-constrained, so baseline is 3. The description goes further by explaining what api_key actually does and what happens when it is absent (x402 payment path), which the schema's bare 'API key' description does not.

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 a specific verb+resource ('Country brief: every reference series we hold for one country') and enumerates the actual content (policy rate, VAT/GST, CPI, taxes, minimum wage, holidays) plus the fields returned per item. This clearly distinguishes it from the single-series siblings get_series/list_series.

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?

'Cheaper than buying the series one by one' implicitly routes the agent away from per-series calls, and the closing sentence names concrete follow-ups (get_changes for polling, register_alert for push) with their conditions and prices. It lacks an explicit 'do not use when you need only one series' statement, so it falls just short of a full 5.

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