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

With no annotations, the description carries the full burden and does meaningful work: it discloses the key side-effect (freezing price, quantity and shipping) and explicitly clarifies a non-behavior ('Qomvia never takes the payment'). It omits auth requirements, whether the frozen values expire, and what the session object contains, which are gaps for a state-creating tool.

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?

Two tight clauses, front-loaded with the action and its effect, then the crucial non-payment caveat and the next step. No filler sentences.

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 tool with no output schema, the description covers the workflow and the safety-relevant caveat that payment happens elsewhere, which is the most important thing an agent needs. It could still mention what the session returns (e.g., a session id for use with complete_checkout) and any expiry, but the essentials are present.

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 description coverage is 100%, so all four parameters are already documented in the schema, making 3 the baseline. The description's mention of price/quantity/shipping loosely maps to qty and shipTo but adds no format or constraint detail beyond the schema.

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 ('Open a checkout session on an offer') and names the exact scope of what it freezes (agent price, quantity, shipping). It also positions itself in the workflow relative to complete_checkout, so an agent can distinguish it from get_checkout_session and cancel_checkout_session without opening a schema.

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 implies the workflow ordering by noting that 'complete_checkout returns the merchant's payment URL', which tells the agent this tool is the precondition step and that payment is a separate call. It stops short of explicitly stating prerequisites or when not to use it, but the routing context is clear.

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