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

Annotations already cover read-only, idempotent, non-destructive and closed-world behavior, so the description's added value is the pagination contract ("follow `next_cursor` while `has_more` is true") and the aggregation semantics — a Dayparting change collapses to one line per campaign with a bid count and percentage range, while a refused bid becomes its own line. That is genuinely useful interpretation guidance beyond annotations, though nothing is said about ordering or result limits.

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?

The action and scope are front-loaded in the first clause, the field inventory follows, and pagination is pushed to the end where it belongs. The sentence is dense with parenthetical asides and the Dayparting special case interrupts the flow, but no sentence is filler.

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 no output schema, the description carries the burden of explaining returns, and it does so thoroughly: per-line fields, before/after values, error text, and the Dayparting and refused-bid edge cases. Ordering of lines and behavior on an invalid operation_id are the only notable omissions.

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%, and the schema already documents limit, cursor and operation_id in detail (including the same list_activity reference). The description adds no format, constraint or semantics for any parameter, so the 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?

"List what ONE operation created, changed or archived" gives a specific verb, resource, and scope, and the line-level enumeration that follows (object, operation, status, keyword, before/after values, Amazon error) makes it unmistakable what this returns. The emphasis on ONE operation separates it from the sibling list_activity, which enumerates operations themselves.

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 closing question "Answers 'what exactly did this rule change?'" plus the operation_id note ("an `id` from list_activity, or one of a rule run's operation_ids") gives the agent a clear prerequisite chain from the sibling tools. There is no explicit exclusion or when-not-to-use statement, so it stops 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.