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

The description discloses a genuinely non-obvious behavioral trait that annotations cannot convey: calling it mutates nothing, it returns a preview plus a confirmation link, and only the merchant on that page can commit the change. It also states the money unit convention. The one caveat is that readOnlyHint=false sits slightly at odds with "changes nothing," though this is reconcilable since the tool is the first step of a write workflow rather than a pure read.

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 short sentences, front-loaded with the purpose and the key behavioral clarification, with no filler. The money-units sentence is somewhat redundant given the schema but is brief enough not to be wasteful.

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 2-parameter tool with full schema coverage and annotations, the description is nearly complete: it explains the preview/confirmation return behavior, which usefully compensates for the absent output schema. It could still note the permissions or who may invoke it, but nothing critical to correct invocation is missing.

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%: flatRate and freeAbove are fully documented in the schema, including the minor-units convention and the null/never semantics. The description's "Money is integer minor units (cents)" merely restates what the schema already says, so it adds no meaning beyond the structured field.

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+resource ("Set the fallback delivery price") that is immediately distinguishable from the sibling shipping tools (shipping_set_method, shipping_set_zones, shipping_set_countries), which govern other aspects of shipping. It further clarifies the fallback semantics so the agent knows exactly what resource is being targeted.

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?

The description gives no explicit when-to-use guidance, no when-not-to-use conditions, and names no alternative (e.g. shipping_set_method). The only contextual hint is the word "fallback," and the surrounding condition (no delivery method covers the order) is supplied by the schema, not the description.

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