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

Annotations only declare the write/safety profile, so the description earns credit for adding real behavior: idempotent retry with the same checkout and token, reuse of existing authorized/processing/paid payments, and instruction to follow the returned status and messages. It does not discuss auth requirements, rate limits, or failure modes beyond interruption.

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?

Four dense sentences, all of which carry actionable information, with the preconditions and identifier mapping front-loaded. No filler, though the sentences are long enough that key constraints compete for attention.

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 write tool with nested objects and an output schema, the description covers preconditions, idempotency, reuse of existing payments, and where to read the outcome. What remains thin is the distinction from sibling payment tools, which the description never addresses.

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%, so baseline is 3, but the description adds genuine meaning: it maps the order ID onto checkout_session_id, states a shared payment token (spt_...) is acceptable, and warns against resending the document or addresses. It does not further clarify the nested buyer/billing_address shapes, which the schema already covers.

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: pay/finalize an already-prepared checkout session with a payment token. It clearly scopes the tool to the post-approval step, though it never names the sibling pay_order it must be distinguished from. Minor ambiguity in 'Pass the order ID as checkout_session_id' blurs resource naming slightly.

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?

Gives a clear triggering condition ('after the buyer approves the prepared order and total') and an explicit do-not ('do not resend the document or addresses'), plus retry guidance on interrupted requests. It stops short of naming an alternative tool or stating when this should not be used instead of pay_order.

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