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

Annotations already declare this a safe, idempotent read, so the bar is lower. The description adds real context by disclosing the shape of the data and the exact pricing basis used for comparison (1 GB · 7 days on a one-country route), which tells the agent what the numbers mean and how they can be used in a recommendation.

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?

It is a single sentence with no wasted padding, and the core content (networks + reference price) is front-loaded. The nested parentheticals make it dense and slightly meandering, but nothing is superfluous.

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 return contents, and it does so adequately: per-network operator name, 4G/5G availability, and a reference price. It leaves the precise comparison semantics (is the listed price the cheapest tier? does it change with currency/bucket?) to inference, but an agent can call it correctly.

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 the schema already explains destination, language, bucket, and currency. The description reinforces the single-country scope for destination but adds no syntax or format detail beyond what the schema provides, so 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 precisely (mobile networks for one country) and enumerates the returned fields the agent cares about: operator name, 4G/5G, and a reference-route price. It is distinguishable from price_grid and quote_route by its per-network, single-country scope, though it never names a sibling explicitly.

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 clause 'so you can say which network is the cheapest and what the others add' implies the use case: comparing networks within one country. There is no explicit when-not guidance, no mention of how this differs from price_grid or quote_route for other pricing questions, and no stated prerequisites.

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