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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds real context beyond that: a hard cap of 10 results and that each match carries an id plus an eSIM-availability signal. It stops short of stating ordering or empty-result behavior, which matters slightly for an open-ended name query.

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, zero filler, with the primary purpose first and the return shape second. Nothing repeats the name or title verbatim.

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 one-parameter read-only lookup with no output schema, the description covers what it does, what it returns, and the result cap. The only gap is not saying what an empty result means (unknown country vs. no eSIM coverage) — a minor but real ambiguity for a lookup tool.

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 single parameter's description already gives examples ("Turkey", "TH"), so the schema does the heavy lifting. The description's "by name or ISO code" corroborates but adds nothing new — e.g. no note on partial/fuzzy matching or case sensitivity for name lookups, which is the one ambiguity a caller would actually hit.

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?

Specific verb + resource ("Find countries") plus the secondary purpose of checking eSIM availability, which is the actual business question. The result cap and id field are stated, so an agent knows exactly what comes back without opening the schema. Siblings (package/registration tools) operate on different resources, so no confusion arises.

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?

Usage is implied by the wording — a lookup-by-name-or-code tool used before checking packages or registration rules — but there is no explicit "use this when…", no mention of what to do on zero matches, and no pointer to list_packages or sim_registration_rules as the follow-up step. Adequate, not instructive.

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