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

No annotations are provided, so the description carries the full burden. It reveals that this is a read-style 'Fetch' operation and adds important context that nothing is ordered until the user completes checkout and that the eSIM is emailed automatically. However, it does not describe return format, error behavior, or confirm whether this call has any side effects.

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 front-loaded with the core purpose and keeps the purchase-flow guidance tight and actionable. Every sentence adds useful context; there is no redundancy or 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?

Given the simple two-parameter schema and the clear purpose statement, the description is nearly complete. It explains the source of the id and the downstream purchase flow, though with no output schema it could still say a bit more about what the returned 'full details' contain.

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 the schema already documents plan_id and currency fully. The description adds only the useful detail that the plan_id comes from search_esim_plans, which is a small value add over 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?

The description clearly states 'Fetch full details of a single Siima eSIM plan by its id', giving a specific verb, resource, and single-item scope. It also references search_esim_plans as the id source, which distinguishes it from the sibling search 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 tells the agent where the plan_id comes from ('from search_esim_plans') and what to do next for purchases ('call create_checkout_link...'). It does not explicitly say when not to use this tool, but the workflow context makes the intended usage clear.

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