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

Annotations already establish readOnly=false, idempotent=true, destructive=false, so this is a safe additive write. The description adds real context beyond those annotations: the scanner re-checks tracked keywords on its passes and top-10 positions feed the rank history, plus the KEYWORD_TRACK_CAP limit and the scope requirement. It doesn't say what happens when the cap is exceeded (error vs. silent truncation), which is the one meaningful gap.

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?

Two dense sentences, front-loaded with the core action, followed by the consequences and the auth prerequisite. No filler or restatement of the tool name.

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 two-parameter mutation tool with no output schema, the description covers the action, the cap, downstream effects, and the auth scope. What's missing is the observable outcome: whether the call returns the accepted keywords, skips duplicates silently, or fails when the cap is reached.

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 both productKey and keywords are already documented, including the trim/lowercase/dedupe normalization. The description adds only the cap concept, which is stated in terms of KEYWORD_TRACK_CAP rather than the array's maxItems of 100, so it does not materially deepen parameter meaning.

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 states a specific verb and resource ('Adds keywords to a product's rank-tracking board') and ties the resource to the downstream consumer ('the rank history get_keyword_ranks reads'). That makes it distinguishable from remove_tracked_keywords and from the read-side siblings without needing the schema.

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 clear operational conditions: the per-product cap and the required 'rescan' key scope. It does not explicitly name an alternative tool or say when not to add keywords (e.g., duplicates already tracked), so it stops short of full routing guidance.

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