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

No annotations are provided, so the description carries the full burden. It does signal that this is a complete read ('List all') with a described return shape, but says nothing about permissions, rate limits, or whether the list is cached/static.

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. The purpose comes first and the downstream usage tip follows, which is the right front-loading for a lookup tool.

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 no output schema, the description must convey the return shape, and it does so at a high level (slug, English name, region). Slightly more precision on field names would make it fully self-sufficient, but nothing essential is missing for a zero-parameter list call.

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 takes zero parameters, so the baseline is 4. The mention of the 'country' argument applies to sibling tools, not this one, and is a useful cross-reference rather than a gap.

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 and resource ('List all Alt eSIM destinations') and immediately clarifies what each entry contains (country/region slugs, English names, region). It also names the sibling tools that consume the output, so an agent can place it precisely in the workflow.

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 second sentence gives a concrete usage rule: take a slug and pass it as the 'country' argument to search_esim_plans or recommend_plans. That is clear context for when to reach for this tool, though it doesn't explicitly exclude alternatives or state prerequisites like auth.

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