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

Annotations already declare readOnly/idempotent/non-destructive, and the description earns credit beyond them by spelling out the downstream consequence: nothing is ordered by this call, the shopper reviews, adds shipping and pays on knobs.co. It also says what comes back (line items with list prices and subtotal), which matters since there is no output schema.

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?

Two dense sentences with no filler; the core action and the 'nothing is ordered' caveat are front-loaded, and the return-value sentence follows naturally.

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?

Covers purpose, mutation-safety, provenance of inputs and the shape of the response, which is enough for a 3-param tool with no output schema. Minor gaps remain, such as link expiry or failure behavior for invalid variant ids.

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 schema already documents items, variant_id, quantity, note and plan_url. The description only reinforces the provenance of variant ids, adding little meaning beyond the existing field descriptions; baseline 3 applies.

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 concrete transformation (variants + quantities -> a Knobs.co cart link) with a named resource and the end-to-end context (shopper opens, reviews, pays on knobs.co). It also names the upstream siblings (search_catalog, get_product, build_plan) that produce the ids, so an agent can place it precisely in the 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?

Clear about the situation that calls for it: you already have chosen variants and quantities and want a pre-filled cart. It does not name an alternative tool or state an explicit exclusion ('use X instead when...'), which keeps it short of a 5.

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