create_billing_portal

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

The description claims 'This call itself changes nothing,' which contradicts annotations readOnlyHint=false and openWorldHint=true. Creating a Stripe Billing Portal session is an external side effect, so the description is misleading about the tool's behavioral profile. This is a direct annotation contradiction.

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?

Three compact sentences front-load the primary outcome, then cover prerequisites, failure handling, and side-effect expectations. Every sentence earns its place with no filler or repetition.

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 zero-parameter operation with no output schema, the description covers the returned URL, the key failure condition, and the required prerequisite. It is nearly complete, but the contradictory 'changes nothing' claim weakens the overall context an agent can rely on.

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 input schema has zero parameters and 100% schema coverage, so there is no parameter gap for the description to fill. The description still adds useful context by noting the implicit target is the 'active organization' and that no inputs are needed.

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 uses a specific verb and resource: 'Create a Stripe Billing Portal session' and states the returned value (its URL) and the end-user purpose (managing payment methods, invoices, and subscription). It also distinguishes itself from the sibling create_billing_checkout by scoping to an existing billing account.

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 prerequisites: an owner API key and an existing billing account. It names the exact failure mode (no_billing_account), explains when the tool cannot be used (org has never checked out), and directs the agent to call create_billing_checkout first. This is explicit when-to-use and when-not-to-use guidance.

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