open_billing_portal

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

No annotations are supplied, so the description carries the full burden; it does disclose the return value (a portal URL) and the important behavioral constraint that plan changes must never be performed by an agent. It leaves out portal URL lifetime/single-use behavior and whether the customer must be authenticated to generate one, which matters for a credential-adjacent tool.

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, front-loaded with the capability and then the hard constraint plus fallback. Every clause carries decision-relevant information; nothing is redundant.

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 two-parameter, no-output-schema tool, the description covers purpose, action scope, and the critical prohibition on plan switching. The remaining gap is invocation detail around license_key and URL expiry, which is meaningful but secondary.

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 only 50%: return_url has a stated default, but license_key is completely undocumented in the schema. The description mentions neither parameter, so an agent gets no guidance on what license_key must be (the paying customer's key?) or when to override return_url.

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 (get a Stripe Billing Portal URL) plus the concrete customer actions it enables: update card, see invoices, cancel. That is enough for an agent to distinguish it from the many printing/design siblings that dominate the tool list.

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 names the excluded case ('Plan switches are not in the portal and never made by an agent') and routes to a named alternative: explain the plans, then send the person to https://app.kiln3d.com/settings/billing. This is a real when/when-not/alternative split, not an implied one.

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