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

Annotations already declare readOnlyHint=true, idempotentHint=true, and non-destructive, which are consistent with generating a link rather than creating a server-side record. The description adds real behavioral context beyond annotations: the payment happens off-platform and the link is meant to be shared with the user.

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 written sentences, front-loaded with the outcome (a link), then the user flow, then the parameter branching. 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?

With no output schema, the description correctly states what is returned (a link URL) and how the consumer uses it. It covers the composite parameter requirements for both enum branches. Minor gap: no mention of error/failure behavior, but otherwise complete for the task.

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 80%, but the description adds the key conditional logic the schema cannot express — which parameters to pass based on the 'type' enum value. That mapping (esim→plan_id; topup→phone/operator_code/send_value) is genuine value beyond the field descriptions.

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 a slashtel.com link) with the scope of what's pre-selected (eSIM plan or top-up). The mention of get_topup_plans and get_esim_plans implicitly distinguishes it from the plan-listing siblings, so an agent can tell it isn't a lookup 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?

Gives explicit workflow guidance — share the link, user enters email and pays on site — and branches by type ('esim' → plan_id; 'topup' → phone, operator_code, send_value). It lacks explicit when-not-to-use conditions, but the conditional parameter routing is strong usage guidance.

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