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

Annotations already declare readOnlyHint and idempotent, so the safety profile is covered; the description adds meaningful context beyond that by stating the user signs in and pays on simvito.com and that nothing is charged here. It also discloses what the result contains — price in the user's currency totalled for the quantity, plus payment methods for that currency.

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?

Two front-loaded sentences with no filler: the first states the action and result contents, the second states the payment boundary. Nothing is redundant or buried.

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 an output schema present, the description need not detail return fields, and it correctly focuses on the link, the payment boundary and the currency/quantity semantics. The only gap is routing guidance among the adjacent checkout siblings, which is not addressed.

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 every parameter including locale, currency, quantity, trip_days and destination is already documented in the schema with defaults, ranges and examples. The description adds only the notion that the price is totalled for the quantity, which is marginal beyond the schema text, so the baseline 3 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?

The description uses a specific verb and resource — 'get the simvito.com checkout link for a plan' — and names the source tools search_plans and plan_trip, so an agent can tell it apart from generic plan-browsing siblings. It does not differentiate itself from the closely named start_checkout or get_checkout_options, which limits it to a 4.

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?

Usage is implied by 'for a plan from search_plans or plan_trip', which gives the upstream step but not an explicit when-to-use rule. There is no guidance on when to prefer get_checkout_options or start_checkout instead, so the agent must infer the ordering from sibling names alone.

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