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

With no annotations, the description carries the full burden. It discloses that counts and prices are limited to country plans for comparability, and notes that many more countries are reachable via multi-country plans, which is a meaningful scoping constraint. It doesn't mention pagination or ordering, but for a simple list tool, this is adequately transparent.

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 purpose and followed by a necessary scope caveat. No wasted words; every clause adds value.

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?

Given no output schema, the description does a good job indicating what the response contains (countries, counts, prices) and the ISO code format. It also explains the scope limitation clearly. Minor gaps exist around ordering and exact response shape, but for a low-complexity list tool this is sufficiently complete.

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 schema already fully documents the currency parameter, including enum values, default, and description. The tool description adds no additional semantic detail about the parameter, but schema coverage is 100%, so the baseline of 3 is appropriate.

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 countries with single-country eSIM plans, including plan counts and cheapest total price. It specifies the ISO 3166-1 alpha-2 format for country codes and distinguishes itself from sibling list_regions by explicitly noting the scope limitation to single-country plans.

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 explicitly explains when to use this tool (for single-country plans) and directs users to list_regions for multi-country plans. This provides clear when-to-use vs. alternative guidance, satisfying the highest bar for this dimension.

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