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

Annotations already indicate idempotency and destructiveness, and the description adds valuable behavioral context by explaining the return contents (line items, total, payment options) and the two possible continuation flows. It does not contradict the annotations, though it could further clarify the implication of destructiveHint, but the added flow guidance is substantial.

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 well-structured with a clear opening sentence and a numbered breakdown of the two payment paths. Every sentence contributes to understanding the tool's purpose and follow-up actions, though it is slightly longer than strictly necessary; still, the structure aids readability and comprehension.

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?

Given the presence of an output schema (which handles return details) and annotations (handling idempotency/destructiveness), the description focuses on the essential workflow context: what the tool does, what it returns, and how to proceed via either payment path. This makes the description complete for an agent to correctly select and invoke the tool.

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 input schema already covers both parameters with descriptions (100% coverage), so the description adds little beyond reaffirming that authentication is required. It does not provide additional syntax, constraints, or formatting details beyond what the schema offers, hence a baseline score of 3 is appropriate.

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 clearly states the tool's function with a specific verb and resource: 'Initiate a checkout session for a medication order.' It also distinguishes itself from sibling tools by explaining the two payment paths and referencing checkout_complete and checkout_status as subsequent actions, making its role in the workflow explicit.

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 provides explicit when-to-use guidance by detailing two payment paths: if ACP/SPT is available, use checkout_complete; otherwise, fall back to payment_url and poll with checkout_status. It also states the prerequisite of authentication, clarifying the context for invoking this tool.

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