roamzy_list_countries

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds useful context about the tool being a 'reference table' and the universal eSIM model, which goes beyond annotations without contradicting them. It does not describe output format, but the output schema covers that.

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?

Two sentences, front-loaded with the primary action and scope. Every phrase adds value: the rate card nature, the 193 countries, the USDT currency, and the usage guardrails. No redundancy or fluff.

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 no-parameter, read-only list tool with an output schema, the description fully covers scope (all 193 countries), semantics (per-MB rates, USDT), and usage intent. It also provides the 'universal eSIM' context, making the tool's role clear in the broader product flow.

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?

The tool has zero parameters, so baseline is 4. The description appropriately focuses on the tool's purpose rather than parameters, as there is nothing to clarify. No parameter documentation needed.

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 clearly states the tool lists all 193 countries with Roamzy per-MB rates in USDT, using specific verbs ('List') and resource ('countries with rates'). It also distinguishes itself from a product catalog, making its purpose unambiguous and differentiated from siblings like list_esims.

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?

Explicitly instructs when to call ('what countries are supported' or 'show me rates') and when not to ('don't volunteer it during a purchase flow'), providing clear usage context and exclusions. This is a model example of usage guidance.

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