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

Annotations already cover the safety profile (readOnlyHint=true, idempotentHint=true, destructiveHint=false). The description adds some behavioral context: pay-as-you-go billing, 0.1 GiB billing increments, and no sign-in required. However, it doesn't explain rate limits, caching behavior, or whether prices are guaranteed or estimates only.

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?

The description is concise and front-loads the core purpose. Sentences earn their place, though the phrasing is slightly awkward in places (e.g., 'Pay as you go per GB' could be tighter). Overall efficient.

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 read-only pricing tool with annotations covering safety, no output schema, and partial schema coverage, the description is adequate but not complete. It should clarify what the country parameter expects (ISO code vs name) and whether the returned price is an estimate or final. As is, an agent has enough to call it but not enough to interpret results confidently.

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 67%, so the schema documents the 'gb' and 'currency' parameters, but 'country' has no schema description. The description mentions an optional gb value and 0.1 GiB billing steps, adding some semantics, but doesn't fully compensate for the country parameter gap. Baseline 3 is appropriate.

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 ('Price') and resource ('travel data for a country'), and distinguishes itself from home mobile service pricing. Separates from pricing siblings like get_data_rate and quote_call by its travel/eSIM framing, though it doesn't name those siblings 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?

Provides implied usage with 'Use this when a trip needs data and not a home mobile service,' which gives some context, but does not explicitly name alternatives like get_data_rate or quote_call, nor does it state when not to use the tool.

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