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

It explicitly flags the operation as 'MUTATES' and says it creates a Stripe billing-portal session, adding useful behavioral context beyond the destructiveHint annotation. It also states the return shape, though it does not cover authorization requirements or other side effects such as portal-session expiry.

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 two sentences with no filler. It front-loads the mutation warning, states the tool's purpose, gives the API endpoint, and describes the response, all concisely.

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 simple tool with one required parameter and no output schema, the description is largely complete: it explains the action, the API call, and the returned values. Minor gaps include not mentioning portal behavior after redirect or any prerequisite relationship with a Stripe account, but these are not critical for invocation.

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%, so the parameters are already well documented in the input schema. The description mentions the returned customer_id and url but does not add new meaning to return_url or configuration_id beyond what the schema provides.

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 names a specific action ('creates a Stripe billing-portal session') and the resource ('for a customer to manage their subscription'), making the tool's function immediately clear. It also distinguishes the tool from the many get/list siblings by emphasizing that it is a mutating operation.

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 supplies clear context: this tool is for letting a customer manage their subscription via Stripe's billing portal. It does not explicitly name alternatives or exclusion criteria, but the purpose is specific enough that an agent can infer when to choose it.

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