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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and closed-world, and the description is fully consistent with them. It adds genuinely useful context beyond the annotations: it 'opens nothing by itself' and returns instructions rather than acting, and it explains why browser tools are needed (no public API for non-partners). Missing details such as behavior when the user is unauthenticated keep it from a 5.

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 sentences, front-loaded with what the tool does and what it returns, followed by the handoff to browser tools. The closing API sentence is slightly tangential but does justify the browser-automation path, so it earns its place.

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 zero-parameter, no-output-schema guide tool, the description covers what is returned (step-by-step screens/buttons/fields) and the correct next action. It does not describe the return format or how to hand off state to the browser tools, but nothing essential for correct invocation 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?

The tool takes zero parameters and the schema coverage is 100%, so there is no parameter meaning for the description to add. Baseline 4 applies.

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: returns step-by-step instructions (screens, buttons, fields) for buying an eSIM in the user's Airalo account. It also clarifies the surprising part of the name — the tool does not itself perform a purchase. It stops short of explicitly contrasting with airalo_top_up_esim, which also concerns eSIM purchase-adjacent flows.

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?

Clear context for use: the user wants to buy an eSIM, and the follow-up path is spelled out ('then do it with the cotlet_browser_* tools'). The API note implicitly rules out a direct API route. No explicit exclusion against the sibling top-up tool, so an agent must still infer new-purchase vs. add-data.

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