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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds real value on top: what happens when the link is opened (plan added to cart, checkout flow), accepted payment methods, QR delivery by email, and the reassurance that calling the tool charges nothing. It does not cover link expiry or whether the URL is single-use, which would be the remaining operational detail.

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?

Three tightly packed sentences: purpose and input source first, then downstream behavior, then the no-charge caveat. No filler, and the most decision-relevant information is front-loaded.

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 carries the burden of explaining what the agent gets back and what happens next (a checkout link, payment, emailed QR code) and it does so completely. Nothing needed to call this two-parameter tool 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 100%, so both parameters are already documented, including the allowed languages and the id source. The description reinforces package_id provenance but adds nothing about the language parameter or format syntax beyond the schema. 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 and resource ('Get a simabroad.com checkout link for one eSIM plan') and ties the input to its origin tool, naming search_esim_plans explicitly. An agent can distinguish this from list_destinations and search_esim_plans without opening a 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?

Clearly states the context of use: call it with the id returned from search_esim_plans to hand a traveler a checkout link. It implies the alternative (search first, then link) but never states an explicit exclusion or fallback, so it falls just short of a 5.

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