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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false), so the description's real job is describing what comes back, and it does list the returned data categories. It stops short of return shape, pagination or how a missing/unsupported destination behaves, so it adds moderate value rather than rich context.

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 dense sentence that front-loads the returned data categories with zero filler. It lacks a leading verb, which slightly hurts readability, but nothing is wasted.

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 is the only source for return content, and it gives a reasonable field inventory. However, it omits the destination input format and any usage boundary against check_coverage, leaving the agent with unresolved ambiguity for a tool in a crowded sibling set.

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 only 50%: locale is thoroughly documented in-schema, while destination has no description at all. The phrase 'Coverage (ISO country codes)' is ambiguous about whether ISO codes describe the destination input format or the returned coverage, so the description only partially compensates for the 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?

The description enumerates exactly what the tool returns for a destination: coverage, mobile operators, top-up availability and entry price. That is a clear resource-and-attributes statement, but it never contrasts itself with the sibling check_coverage, which on name alone sounds like it may overlap.

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?

There is no when-to-use guidance, no prerequisites, and no routing to alternatives such as check_coverage, list_destinations, or search_plans. The agent is left to infer usage entirely from the name and the list of returned fields.

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