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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real value beyond that: the search is bounded to destinations eSIM SOS actually sells (a meaningful scope constraint) and it discloses the return format (country codes). It does not cover miss/ambiguity behavior, but that is a minor gap against the annotation coverage.

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, no filler. The capability and input forms come first, and the downstream consumer (list_plans) is placed at the end where it belongs.

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 a single parameter and no output schema, the description carries return-value disclosure itself, and it does ('Returns country codes'). An agent has everything needed to call it, though behavior on no-match or ambiguous names is unstated.

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 the schema example ("Turkey", "Турция", "TR") already demonstrates name and ISO-code input. The description's 'name in English or Russian, or by ISO code' largely restates the schema, adding only marginal clarification, so the 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?

States a specific verb (find) plus resource (travel destination/country) and narrows the scope to destinations sold by eSIM SOS. It also says exactly what comes out — country codes — and routes the agent to list_plans, so it is distinguishable from siblings without opening a schema.

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?

The workflow is made explicit: this is the lookup step that produces the country codes list_plans consumes. There are no exclusions or 'use X instead' statements, but the context for when to reach for it is clear.

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