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

Annotations already provide readOnlyHint, openWorldHint, and idempotentHint, so the bar is lower. The description adds useful behavioral detail: polling cadence, the fact that no personal data is ever returned, and the dependency on the session_id from create_checkout. It does not specify what happens before payment, but the 'once paid' phrasing plus polling guidance covers the main behavior.

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 a bit longer than strictly necessary, largely because it repeats 'create_checkout' several times. However, each sentence carries distinct information: what the tool returns, when to call it and how often, and what data is never exposed. The main purpose is front-loaded.

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?

There is no output schema, so the description carries the burden of explaining the return value; it does so by stating the delivery link is returned once the checkout is paid. Combined with the polling guidance, that is sufficient for a one-parameter read tool. A minor gap is the lack of any mention of the unpaid/error response shape, but the overall usage is clear.

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 schema already describes the parameter and its 'cs_' prefix, establishing a baseline of 3. The description adds contextual meaning by tying the parameter to create_checkout's return value and emphasizing that it cannot be replaced by an email or search-based lookup.

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 ('Check') and a specific resource (a checkout created by create_checkout) and explains what happens once it is paid: the delivery link is returned. It differentiates itself from the create_checkout sibling by making clear this is the read-side follow-up, not the creation step.

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 explicitly says to call it after handing out the checkout URL and warns against busy-waiting by advising a few seconds between calls. It also states the required input (session_id) and what is not possible (no listing/searching/email lookup), giving an agent clear boundaries on when and how to use it.

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