create_billing_portal

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

Annotations indicate readOnlyHint=false (mutation), openWorldHint=true, idempotentHint=false, destructiveHint=false. The description does not contradict annotations. It adds value by explaining the outbound call to Stripe, that it creates a new portal session each time (non-idempotent), and that no state changes until the user acts in the portal. This goes beyond the annotations and is helpful for the agent.

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?

The description is three sentences, each earning its place. It front-loads the core action and output, then adds usage guidance and behavioral transparency. No filler or redundancy.

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?

The tool has no parameters and no output schema, so the description carries the full burden. It explains the requirement, the failure mode, the prerequisite, the side effects (non-idempotent), and the fact that no state changes until user action. This is complete for an agent to decide when and how to call the tool 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?

The schema has no parameters, and description coverage is 100% (vacuously). Since there are no parameters, the description doesn't need to add parameter semantics. The baseline is 4 for 0 params, and the description is clear about the tool's function, so a 4 is appropriate.

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 clearly states the tool's purpose: to create a Stripe Billing Portal session for the active organization and return its URL. It specifies the action, resource, and output. It is distinct from sibling tools like create_billing_checkout, which is for initial checkout, and get_billing_info, which is for retrieving billing information.

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 description explicitly states when to use the tool: requires an existing billing account, and an org that has never checked out fails. It also tells the user to call create_billing_checkout first if needed. This clearly differentiates from alternatives and provides the necessary context for when not to use it.

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