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

Goes well beyond the annotations: discloses that creating the session does not charge a card, that local billing bypass grants Pro immediately with a console URL instead of a Stripe URL, and that a stripe_not_configured error is returned when unconfigured. It also spells out auth requirements and explicitly denies minting a company or aa_ secret.

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?

Dense but front-loaded: the primary action leads, followed by auth, side effects, and bypass behavior. Every sentence carries distinct behavioral information, though the bypass/error details make it longer than strictly minimal.

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 no output schema, the description covers the return value ('Returns url'), the failure mode, and the bypass alternative URL. An agent has everything needed to call 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 100% and the single 'interval' enum already documents month/year with prices. The description only restates 'optional interval month or year' without adding syntax or behavioral detail beyond the schema, 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?

States a specific verb and resource ('Create a Stripe Checkout session') plus the actor and goal ('for the authenticated company so a human can subscribe to Pro'). It clearly distinguishes itself from billing_machine_pay and billing_portal by naming them.

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?

Explicitly routes the agent: 'For prepaid purchase instructions, use billing_machine_pay' and 'To manage an existing subscription, use billing_portal.' It also states what credentials are accepted versus rejected (no console session, no bootstrap token).

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