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

Annotations already declare the full safety profile (readOnlyHint, idempotentHint, destructiveHint=false, closed-world), so the description need not restate it. What the description adds is mostly return-content detail (which fields appear) rather than behavioural traits — no mention of pagination, result size, or whether all countries are always returned, though 'Every country' does imply a complete, unpaginated set.

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 first front-loads what the list contains, the second states the use case. The parenthetical clarifications (5 Mbps, cheapest network) are dense but earn their place by defining the price basis.

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 usefully enumerates the returned fields and the pricing baseline, which is the main thing an agent needs. It omits pagination/volume expectations and does not relate the optional locale parameters to the returned link locales, but nothing critical for a read-only list call is missing.

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 description coverage is 100%, so bucket, currency, and language are all fully documented in the schema itself. The description mentions none of them and adds no syntax or interaction detail (e.g. how bucket overrides language), 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?

The description names the resource (every country roamflat builds a Flat for) and enumerates the returned fields (network count, 5G/25-50 Mbps availability, starting price per day at 5 Mbps on the cheapest network), so the agent knows exactly what this list contains. It does not explicitly distinguish itself from potentially overlapping siblings like price_grid, which is the only gap.

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?

'Use to check coverage or compare countries' gives a clear positive usage context that maps directly to the tool's content. It does not name a when-not condition or point at an alternative sibling (e.g. price_grid for deeper pricing comparison), so routing between overlapping tools is left to inference.

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