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

Annotations only declare the generic mutation profile (readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false). The description adds genuinely useful behavior beyond that: payment is completed on an external Mollie page and never in the chat, and the tool returns a payment link rather than a completed transaction. It does not address what happens on repeat calls (duplicate checkouts) or any auth/rate constraints, so it stops short of full coverage.

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 tight sentences with zero filler, front-loading the action and resource before the buyer fields and the external-payment caveat. Every clause carries information an agent can act on.

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 13-parameter (6 required) open-world mutation tool with a full output schema, the description covers the essentials: what is created, with whose data, and where payment occurs. The return-value explanation is redundant given the output schema, and the lack of prerequisite ordering (plan from get_plans) is a minor remaining gap.

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 enums (service, billing, territory) and defaults is already documented in the schema. The description only echoes the four buyer fields it names and adds no format, constraint, or dependency information beyond the schema, making this the baseline case.

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 (creates) and resource (the secure Mollie checkout), plus the key inputs and the returned artifact (payment link). It is distinguishable from read-only siblings like get_plans and check_obligations, but it never explicitly contrasts with the nearby sibling start_free_trial, which is the obvious free alternative.

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?

The phrase 'the chosen REP27 plan' implies a plan must first come from get_plans, and 'payment happens on Mollie's page' tells the agent this is the paid path, but there is no explicit when-to-use/when-not guidance or named alternative. Usage is implied rather than stated.

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