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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavioral context: base-price arithmetic is not a binding quote, volume terms need an RFQ, and the optional checkout read is restricted to an owner-authorized credential with a matching single line. Return format and pagination are not discussed, but there is no output schema and the read fields are enumerated.

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 sentences, front-loaded with the core capability before the caveats and exclusions. It is dense but each sentence carries distinct information (capability, quote disclaimer, negative-space exclusions). Slight jargon density ('Base-price arithmetic', 'owner-authorized checkout') keeps it just short of ideal.

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 5-parameter read tool with no output schema, the description names the data returned (price, currency, inventory, backorder policy) and explains the optional checkout branch, which is enough for correct invocation. It does not explain error behavior when the SKU/variant or checkout line does not match, which is the main remaining gap.

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 80%, so most parameters are already documented, and the description largely restates the schema: 'exact full SKU and quantity' mirrors the sku and quantity definitions, and 'existing owner-authorized checkout' mirrors the checkout_id and checkout_access_token definitions. The only added nuance is the framing that the checkout read is optional for shipping/tax estimates, which is marginal over the schema.

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 opens with a specific verb and a concrete resource set: read Shopify price, currency, online inventory and backorder policy for an exact full SKU and quantity. The scope constraint ('exact full SKU and quantity') plus the closing list of things it does not create separates it from create_cart, create_checkout and submit_rfq without needing 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 gives clear preconditions (exact full SKU, quantity) and an explicit routing rule: unverified volume terms require an RFQ, which points at submit_rfq. It also rules out mutation use cases by stating it creates no cart, checkout, order or RFQ. What is missing is an explicit comparison against read_shopify_products, the closest read-only catalog sibling.

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