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

readOnlyHint: false already signals a write, and the description adds genuine context: the call is confirm-gated and returns a preview until confirm: true, so the agent knows a real link isn't created by default. This partly overlaps the schema's confirm description but reinforces a critical safety behavior.

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 compact sentences with the purpose front-loaded and the confirm-gating tucked into an efficient parenthetical. Little waste, though the division-of-labor sentence could be tightened further.

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 2-parameter tool with no output schema, the description covers what it creates, who completes payment, and the confirm gate, which is enough to invoke correctly. It could mention discoverability of planId, leaving a minor 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 coverage is 50%: confirm is documented in the schema, while planId is bare. The description says "optionally a specific planId," which adds the optionality and meaning of that field, but gives no format or how to discover valid plan ids. Baseline 3 fits this mixed coverage.

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 (create) and resource (checkout link) scoped to Coach Pro, plus the optional planId. A reader can tell this generates a purchase link rather than performing a sale. It doesn't explicitly name a sibling (e.g. get_coach_pro_pricing), so it stays below a 5.

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?

"Opening and paying is the coach's step" draws a clear scope boundary, clarifying this tool only mints the link and does not complete payment. That is useful usage context, though it never points to the natural prerequisite sibling for pricing.

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