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

With no annotations, the description carries the full burden. It discloses a key behavior: 'If the response has status requires_escalation, share the continue_url with the user.' However, it does not mention side effects, permissions, or other return scenarios, leaving gaps in behavioral transparency.

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 three succinct sentences: purpose, usage context, and special response handling. It is front-loaded with the primary action and contains no redundant information.

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?

The description covers the workflow (after start_checkout), the key parameters, and a critical response branch. It appropriately relies on the output schema for return details. Minor aspects like idempotency are not addressed, but overall it is sufficient for a tool with a clear purpose and schema.

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 the description adds limited value beyond the schema. It mentions the fields in prose but does not add new meaning, formats, or constraints beyond what the input schema already provides.

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 purpose: 'Update a checkout session with buyer information.' It specifies the fields (email, name, shipping address, discount codes) and references start_checkout for sequential context, distinguishing it from sibling tools like start_checkout and complete_purchase.

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?

Explicit guidance is given: 'Call this after start_checkout when the merchant indicates what information is still needed.' This provides clear context on when to use, but it does not explicitly state when not to use it or mention alternative tools beyond start_checkout.

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