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

Annotations already declare a non-read-only, non-destructive, open-world, non-idempotent operation, and the description adds genuinely useful context beyond them: no charge occurs until the user confirms on Stripe, and permission gating behavior for non-owners. It does not mention link expiry or whether repeated calls mint distinct sessions, which is the main remaining behavioral unknown given idempotentHint=false.

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 sentences with no filler: the action and its three modes come first, then the no-charge guarantee and the permission rule. Every clause carries decision-relevant information.

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 one-optional-parameter tool with no output schema, the definition covers the action, the modes, the safety guarantee, and authorization behavior. It is only slightly short of complete because it does not say what form the returned link takes or how long it stays valid.

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 100% and the single parameter is already documented, so the baseline is 3. The description earns an extra point by tying extra_slots to specific modes ('subscribe (optionally with extra slots), add slots to an existing subscription'), clarifying that the same parameter serves both a new and an existing subscription context.

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 gives a concrete verb and resource ('Get a one-click Stripe link for this workspace') and enumerates the three outcomes it can produce: subscribe with optional extra slots, add slots to an existing subscription, or repair a failed payment. That clearly separates it from the read-only sibling get_plan, though it never names that sibling, so it stops short of a top score.

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 when-to-use cases are explicit (new subscription, slot expansion, failed payment recovery) and the eligible audience is stated ('Workspace owners only; other members are told which owner to ask'). What is missing is a when-not-to-use note pointing at get_plan for simply inspecting the current plan or quota.

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