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

No annotations are provided, so the description must carry the full burden. It discloses that it returns a URL and that a human uses it, but it omits side effects (does it create a session?), whether it's idempotent, required permissions beyond the API key, and error behavior. This is a moderate gap for a tool with no structured hints.

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 short sentences with zero waste: the core action is front-loaded, the human use case is explained, and the return shape is stated. Every sentence earns its place.

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 one-parameter tool with no output schema, the description is nearly complete: it explains the return value ({ url }) and the human workflow. It could mention authentication requirements or session validity, but those are minor omissions for this complexity level.

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 coverage is 100% and the single parameter (api_key) is fully documented in the schema. The description adds no additional parameter meaning, so it meets the baseline of 3 when the schema already does the heavy lifting.

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 states a specific verb ('Get') and resource ('Stripe Customer Portal session URL'), making it clear what the tool does. It doesn't explicitly distinguish from sibling tools like start_subscription or account_usage, but the core purpose is unambiguous.

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?

It provides clear context for when to use: 'Your human opens it to update the card, switch between Starter, Pro and Scale, or cancel.' However, it doesn't mention when not to use it or name alternative tools (e.g., start_subscription) for related billing actions.

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