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

Given readOnlyHint=false and idempotentHint=false, the description adds substantial non-obvious context: inventory is NOT deducted (orders go to the pick queue), guest totals are final while VIP totals are estimates billed by invoice, a PromptPay QR confirmation email follows guest orders, and every order without customerKey creates a new customer even for a reused email. It does not contradict any annotation. It stops short of 5 because failure handling beyond guest-address rejection is unstated.

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?

Front-loaded with purpose and mode routing, and most sentences carry real load (permissions, pricing finality, inventory, delivery scope). Minor friction: it announces "Two modes" then lists three (A/B/C), and the customerKey guidance is partially duplicated between the description and the parameter doc.

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 17-parameter, no-output-schema, openWorld mutation tool this is close to complete: it covers mode prerequisites, required guest fields, pricing semantics, delivery geography, dryRun, and one returned value (customerKey). What remains thin is the full response shape — the description notes the key is returned but does not say what else comes back for either mode, leaving the agent to infer.

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?

Despite 100% schema coverage, the description supplies the decisive fact the schema omits: the schema declares zero required parameters, yet the description states shippingAddress, shippingProvince and email are all mandatory for guest orders and that a guest order missing any is rejected. It also constrains shippingProvince to a Thai province and explains that vipItems entries must mirror get_catalog's fishName/status/tier and quantity form verbatim, which is meaning beyond field-level docs.

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?

Opens with a specific verb+resource ("Place an order") and immediately enumerates three distinct order paths (VIP wholesale via lineUserId, guest retail, LINE VIP via personal token URL), each with its own identifying input. It also differentiates from siblings by naming get_catalog (for ordering availability and item shapes) and register_customer (for customerKey), so an agent can tell which tool starts which flow.

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 selection rules per mode: use lineUserId for registered VIPs, customerName/phone/items/address/email for guests, vipItems alone when connected through a personal token URL. It goes further with a procedural rule — "Call with dryRun: true first, show the user the lines and the estimate, and place the order only after the user confirms" — which is exactly the when-and-how guidance an agent needs before a mutating call.

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