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

Goes well beyond the annotations by disclosing the post-call flow (returns a Tanatasa review link, buyer enters delivery details and approves payment) and the retry contract (new idempotency_key per purchase, retain key and guest_token on retries). Annotations only give generic hints, so this added context is genuinely valuable; what's missing is any statement of failure modes or what happens to a partially-abandoned session.

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?

Five tight sentences, front-loaded with the core action, then prerequisites, then the outcome, then retry semantics. Dense but every sentence carries information; no filler.

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?

No output schema exists, so the description correctly explains what comes back (a review link, with buyer-side completion) and it covers the nested items structure and retry requirements. Minor gaps remain around item id format and session expiry, but an agent has enough to call it correctly.

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 only 33%—idempotency_key and the whole nested checkout_session object are undocumented in-schema—so the description has to compensate, and it does: it clarifies that items are product feed IDs and quantities, that optional item metadata (name/price/url/description) is not authoritative, and how idempotency_key is used. It still says nothing about the id format or quantity bounds.

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+resource ('Prepare checkout from product feed item IDs and quantities') plus the notable constraint that no account login is needed. It does not distinguish itself from the equally-named sibling create_checkout, so an agent still has to infer which checkout entry point to use.

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?

Explicitly gives the guest path: call create_cart first and supply its guest_token. That is real when-to-use guidance with a prerequisite, but it never says when to prefer this over create_checkout or the cart tools (get_cart, quote_cart).

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