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

Beyond the annotations, it discloses key behavior: nothing is charged at this step, a checkout link is produced, the person must open it, confirm their number in NUM, and pay on Stripe themselves. This is exactly the operational context an agent needs before calling a non-read-only checkout-starting tool.

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?

The description is short, front-loaded with the core action, and every sentence carries useful information about the flow or the prerequisite. There is no filler.

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?

There is no output schema, and the description compensates by explaining that the result is a checkout link and that payment occurs later on Stripe. Combined with the prerequisite and user-confirmation guidance, it gives enough context to call the tool correctly.

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 schema already documents plan_id and destination with essentially the same guidance found in the description. The description does not add syntax, format, or edge-case meaning beyond the schema baseline.

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 uses a specific verb and resource: starting an order for a plan and obtaining a checkout link. It explicitly ties the plan to esim_find_plans, making its role distinguishable from that sibling tool.

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?

It clearly explains the prerequisite (a plan from esim_find_plans) and adds an explicit instruction to ask the person before calling. It does not name a when-not scenario or alternative beyond the prerequisite, so it falls short of the highest usage-guidance score.

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