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

Annotations already mark the tool as read-only and idempotent, and the description adds substantial behavioral detail beyond them: priority ordering, title/subtitle word removal, dropping of prohibited/trademarked/author-title phrases, and reporting of what did not fit. There is no contradiction with the annotations.

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 description is two tight sentences with no filler. It front-loads the core action and then packs each subsequent clause with a distinct behavioral rule or output note.

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?

The description covers the input, the packing rule, filtering behavior, and the outcome of reporting unfitted phrases. Since there is no output schema, a slightly more explicit statement of the returned structure would make it fully complete, but the invoking context and side effects are sufficiently clear.

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?

With 0% schema description coverage, the description carries the burden, and it does compensate: 'phrases' are the packed input, 'title' and 'subtitle' feed the removal logic, and 'skipTitleWords' relates to title-word removal. It does not fully spell out each parameter's edge-case behavior, but the main semantic roles are inferable.

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 and resource—'Packs keyword phrases ... into KDP's 7 keyword boxes'—and adds a clear constraint ('50 characters each'). It also differentiates the tool from siblings like keyword_research or ads_keywords by focusing on box-filling rather than discovery or advertising.

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 clearly implies the use case: an agent has a candidate phrase list and needs to produce a KDP-compliant keyword-box fill. It does not explicitly name alternatives or exclusion conditions, but the context is clear and not misleading.

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