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

The description adds substantial behavioral context beyond the annotations: it creates an external Shopify checkout, charges nothing, returns a checkout_url for the user to review and pay, validates all details, and aggregates errors. This goes well beyond what readOnlyHint, openWorldHint, idempotentHint, and destructiveHint convey.

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 compact and front-loaded with the core purpose, then efficiently covers return value, payment behavior, pre-call confirmation, and error handling. Each sentence adds distinct value with no filler or repetition.

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 still specifies the critical return value (checkout_url) and the important side effect (nothing is charged). Combined with the detailed input schema, the agent has everything needed to call it correctly, including the required user-confirmation step and error-recovery behavior.

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 high at 88%, so the schema already documents most parameters. The description adds useful meaning by explicitly requiring confirm_digital_file to be true and explaining the no-charge, review-before-pay flow. This is more than the baseline but not needed for every parameter.

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 action ('create a Shopify checkout'), a specific resource ('one personalised poster'), and the key return value ('Returns checkout_url'). It also makes clear this is the final ordering step, distinguishing it from the sibling tools that select posters, fetch forms, or upload photos.

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 gives clear pre-call instructions: read details back to the user and confirm the digital-file expectation by setting confirm_digital_file to true. It also explains how errors should be handled. However, it does not explicitly name sibling alternatives or state when not to use this tool, though the workflow context makes this mostly obvious.

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