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

Annotations declare readOnlyHint=false and idempotentHint=false, so the agent knows this is not a pure read, and the description explains why: it can mint a checkout session and its output varies by subscription state. It also discloses the async unlock via Stripe webhook and the past_due no-checkout rule, which are real behavioral traits beyond the annotations. It stops short of stating explicitly that calling it creates a Stripe session.

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?

Front-loads the core purpose, then branches into per-state behavior in a tight paragraph. Dense but nearly every clause carries state-machine detail; only the parenthetical asides add mild length.

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?

An output schema exists, so return values need not be re-explained, yet the description still clarifies the semantics of checkout_url, next_action, and next_step across states. For a state-dependent billing tool with a non-read-only annotation profile, an agent has everything needed to call it and interpret the result correctly.

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 0% and the single `plan` parameter has no enum in the schema, so the description carries the full burden. It does so by enumerating the allowed values (starter | pro | agency) and the default (starter), adding genuine meaning 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?

States a specific verb+resource (billing status) and immediately adds the second capability (Stripe checkout link when a new subscription is needed). This distinguishes it from siblings like signup, get_provisioning_status, and get_onboarding_status without opening any schema.

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?

Gives explicit state-based guidance: checkout_url is returned for open-signup unpaid, churned, or free/trial-converting workspaces; a past_due workspace gets no checkout and must fix the card in the dashboard. It also says blocking on webhook completion is unnecessary. It does not name sibling tools as alternatives, which keeps it just short of a 5.

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