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

The annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered without the description's help. The description adds a return-content signal (checkout_url) but says nothing about token validity, expiration, or error behavior for an invalid/expired cart.

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?

One compact, front-loaded sentence listing the returned data with no filler or repetition. It is efficient, though it reads as a fragment rather than a fully grammatical statement of action.

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?

With only one parameter, full schema coverage, and no output schema, the description usefully enumerates the returned fields (lines, prices, total, checkout_url) — which is exactly the burden it must carry. It falls short only on edge-case behavior for missing or expired carts.

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 100% for the single cart_token parameter, and the schema already documents its provenance from create_cart. The description adds no format, validity, or lifecycle detail beyond what the schema provides, so the baseline of 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?

The description names the resource (the cart) and enumerates its contents — lines, prices, total, and checkout_url — so an agent knows this is a read of an existing cart. It is distinguishable from write siblings like add_line or set_quantity, though it is phrased as a noun fragment rather than a clear verb+resource statement.

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?

There is no when-to-use guidance, no statement of prerequisites, and no explicit alternative tool named. The only contextual link is indirect: the schema notes cart_token comes from create_cart, implying this follows cart creation, but the description itself offers nothing.

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