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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description usefully adds what the returned URL lets the owner do, but omits notable behavior for a portal link, such as whether it creates a session or whether the URL expires.

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?

A single front-loaded sentence with no filler; the verb and returned artifact lead, with purpose following as supporting detail.

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 no-parameter read tool with no output schema, the description adequately covers what comes back and why. The remaining gap is preconditions (does a Stripe subscription/customer need to exist, and what happens if not?) which an agent would need before a failed call.

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 tool takes zero parameters, so the schema baseline of 4 applies. There is nothing for the description to disambiguate, and it correctly implies the portal is derived from the authenticated caller's account.

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 ("Returns a Stripe Customer Portal URL") and adds what the URL is for: cancel, update card, download invoices. That implicitly distinguishes it from siblings like cancel_subscription and subscribe, though it never names them explicitly.

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?

Usage is only implied by the described capabilities: an agent can infer it's for self-service billing management. There is no explicit when-to-use statement, no exclusion (e.g. 'use cancel_subscription to cancel directly'), and no prerequisite such as requiring an existing Stripe customer.

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