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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered structurally. The description adds genuine behavioral context beyond that: the default window, the hard 90-day cap, and the breakdown dimensions returned. It does not mention rate limits or response size, keeping it short of a 5.

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?

A single tightly packed sentence with the resource, scope, default/cap, and return granularity front-loaded. Nothing is wasted and nothing important is buried.

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 two-parameter read tool with no output schema, the description covers the missing parameter constraint and describes the shape of the result (per-country and per-operator breakdown), which is what an agent needs since returns are not otherwise documented.

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 50%: iccid is documented in the schema, but days is not. The description compensates by stating the default (7) and maximum (90) for days, which is exactly the missing semantic. Minor gap in not explaining the ICCID format requirement, though the schema handles that.

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+resource (daily usage for one eSIM) plus scope and granularity (per-country/per-operator breakdown). It is clear what the tool returns, but it does not differentiate itself from the sibling get_esim_usage, which plausibly overlaps.

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 description supplies operational constraints (default 7 days, max 90) which hint at when it is appropriate, but gives no explicit when-to-use or when-not-to-use guidance relative to get_esim_usage or get_esim_live_status. Usage is implied rather than stated.

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