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

Adds context beyond readOnly/idempotent annotations: the result contains the traveller's private eSIM details, the input link is validated and refused if invalid, and install links work only on the device that opens them.

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?

Front-loaded with the precondition and outcome; dense but each sentence carries information, though the parenthetical URL example adds minor bulk.

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?

Complete for a single-param tool with an output schema: precondition, accepted input, platform requirements, refusal behavior and return content are all covered.

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%, so the baseline is 3; the description adds the accepted syntax (the private eSIM link or the token at its end) and constrains other values as invalid, adding meaning beyond the schema.

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 (one-tap install links for a purchased eSIM) with explicit platform support (iOS 17.4+, Android 10+) and the manual codes, distinguishing it from fetch/get_plans/check_device siblings.

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?

Explicitly says 'After the traveller has paid' as the precondition and instructs that only the private eSIM link from the order confirmation page is accepted: 'any other value is refused.'

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