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

Annotations already declare readOnly, idempotent, non-destructive, and openWorldHint=false. The description reinforces and extends this by disclosing the data source (a built-in table) and, importantly, fallback behavior for unlisted countries (general guidance rather than an error) — real context not present in the 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?

Two tight sentences with no filler; the trigger leads and the behavior follows. The what-it-does statement is deferred to the second sentence, a minor structural nit rather than waste.

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?

An output schema exists, so return-value detail is not needed, and annotations carry the safety profile. Trigger, source, and unlisted-country fallback are all covered; the only real gap is routing against overlapping siblings such as list_country_networks.

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?

With one parameter at 100% schema description coverage, the schema already documents "country" with an example. The description adds nothing about expected format (ISO code vs. name), aliases, or ambiguity handling, 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 names a specific resource (a country fact sheet covering mobile networks, eSIM support, Wi-Fi) and a concrete trigger, so an agent can tell what it returns. However, it never distinguishes itself from close siblings like list_country_networks, check_coverage, or find_free_wifi, which cover overlapping ground.

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?

"Use when the user asks about mobile networks, eSIM support, or Wi-Fi in a country" is an explicit, actionable trigger. There is no when-not guidance or alternative routing despite significant overlap with network-listing and coverage-checking siblings, so it stops short of a 5.

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