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

No annotations are provided, so the description carries the full behavioral burden. It does disclose a meaningful trait beyond the schema — that pricingUnit is 'per_day' and the customer chooses the day count at ordering time — but it omits whether this is a read-only catalog, whether auth is required, and currency or availability caveats.

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 short sentences, front-loaded with what the tool returns, and the pricing note is supplementary rather than buried. Slightly telegraphic wording but nothing 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?

For a one-parameter, read-only catalog tool with no output schema, the description conveys the essential shape of the result (retail eSIM data plans for one destination) and the pricing model. What is still missing is any note on read-only status, currency, or what fields a package record contains.

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 100% and the single parameter is documented there ('A locationCode from list_esim_destinations, e.g. "ES"'), so the schema does the heavy lifting. The description adds no syntax or format detail for the location parameter, matching the baseline of 3 when the schema is complete.

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 a specific resource ('eSIM data plans') and scopes it to one destination at retail pricing, which lets an agent distinguish it from order_esim or quote_esim. However, it never uses an explicit listing verb and does not name any sibling, so differentiation is inferred rather than stated.

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 explicit when-to-use or when-not-to-use guidance. The only routing hint is indirect: the schema says the location value comes from list_esim_destinations, implying this tool is a follow-on step, but the description itself gives no context about when to call it versus quote_esim.

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