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

Annotations already declare idempotentHint=true, destructiveHint=false, and readOnlyHint=false, so the description's idempotency sentence largely restates structured data. It does add one piece of beyond-schema context — that additions are 'subject to plan limits' — but leaves unexplained what happens when the limit is hit (error vs. silent skip).

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 efficient sentences with the core action front-loaded and the idempotency note secondary. No 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?

Given an output schema exists, return values needn't be explained, and annotations cover the safety profile. The remaining gap is behavioral nuance around plan-limit failures and store selection, which the description gestures at but does not resolve.

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 coverage is only 33%, so the description should compensate more than it does. It maps loosely onto all three parameters ('specified competitor apps' → appIds, 'project's keyword tracking' → projectId, 'one store' → storeProvider), but adds no array-size, format, or defaulting detail beyond what the schema and storeProvider's own description already provide.

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 — adding competitor apps to a project's keyword tracking — which clearly separates it from add_keywords (keywords) and suggest_keyword_competitors (suggestions). It could go further by naming those siblings explicitly, but the resource distinction is strong enough for correct selection.

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 phrase 'for one store' and 'subject to plan limits' hints at the operating context, but the description never says when to prefer this over suggest_keyword_competitors or how it relates to add_keywords. Usage is implied rather than directed.

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