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

The description adds real behavioral value beyond the annotations - it explains the deferred model (preview + confirmation link, merchant-only activation), which the structured fields do not convey. But it directly conflicts with readOnlyHint=false by asserting 'Calling this changes nothing', so the agent receives contradictory safety signals.

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, front-loaded sentences with no padding; the core action leads and the safety caveat follows. The money-units sentence does not map to any parameter here, so it is slight wasted space, but overall the structure is tight.

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?

There is no output schema, and the description compensates well by stating what the call returns (a preview of changes and a confirmation link). With a nested filter object fully described in-schema and no output schema to carry return semantics, this is nearly complete, missing only what happens on the confirmation page.

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%, so every parameter (name, filter, percentBps, startsAt, endsAt) is already documented in the schema and the baseline is 3. The description adds nothing for the actual parameters - the 'integer minor units (cents)' note refers to money, yet no parameter in this schema takes a money amount, making it orphan guidance rather than parameter clarification.

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 specific verb+resource ('Run a sale') that an agent can map to the catalog-discount domain. It is clear what the tool does, but it never names or contrasts itself with the closer siblings (discounts_coupon, promotions_set_active, promotions_edit), so sibling disambiguation is left to inference.

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 implies when to use it by describing the confirmation flow ('Only the merchant, on that page, can make it happen'), which signals this is a request-a-sale step rather than an immediate effect. However, it gives no explicit when/when-not guidance and never points to discounts_coupon or promotions_* as alternatives.

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