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

Annotations only declare the mutation and open-world profile; the description adds genuinely useful behavior beyond that: the returned checkoutUrl/sessionId/expiry, that the buyer pays by card, and that tax is added by AgentaOS. It stops short of stating auth/permission requirements or whether the session can be cancelled or re-issued.

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, front-loaded with the core action and value of the return payload. The opening 'Create a checkout session. Creates a one-off checkout...' is mildly redundant, but nothing else is wasted.

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?

With no output schema, the description correctly carries the return-value burden (checkoutUrl, sessionId, expiry) plus payment and tax behavior, which is enough for a five-parameter tool. It leaves out error/expiry handling and currency defaults, minor gaps.

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% and each of the five parameters is documented inline, so baseline 3 applies. The description only echoes amount ('for an amount') and adds no meaning for email, currency, business, or description beyond what the schema already says.

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 ('Create a checkout session') and immediately narrows scope to 'a one-off checkout for an amount', which separates it from the subscription siblings. An agent can act on this without opening the 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?

It provides a clear follow-up path ('Follow up with agenta_pay_get') which gives some routing signal, but never states when to use this tool versus alternatives such as agenta_products_create or the subscription tools, nor any exclusions or prerequisites. Usage is implied rather than explained.

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