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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is fully covered. The description adds the 8 × 8 cap (also encoded in the schema) and the useful consistency note that prices match quote_esim, but discloses no pricing edge cases, currency behavior, or latency/cost traits beyond that.

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 tight sentences, front-loaded with the capability and its cardinality bound before the use case. The closing note on quote_esim pricing parity is short and earns its place by clarifying result consistency.

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 lookup with rich schema descriptions and no output schema, the description covers scope, limits and intended use adequately. It could be fuller on how the grid result is shaped or what currency/bucket defaults resolve to, but nothing critical to calling it correctly 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 86%, so the schema already documents gb, days, bucket, language, networks and destination in detail. The description adds only the aggregate 8 × 8 bound and 'one country per eSIM', which the schema largely repeats; baseline 3 is appropriate when the schema does the heavy lifting.

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 resource (prices) with explicit scope: a grid of GB × days combinations for one country in a single call, capped at 8 × 8. It also names the sibling quote_esim and ties its pricing to it, so the agent can distinguish batch-grid pricing from a single quote without opening either schema.

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?

Gives concrete intent ('compare with other providers' or 'find the best fit for a trip') and implies the batch use case, which is clear guidance. It stops short of an explicit when-not rule (e.g. 'use quote_esim instead for a single combination'), so it lands at a strong 4 rather than a full 5.

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