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

Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false. The description adds valuable context beyond these: it states that country/language are inherited from the site, that it requires an active subscription, and that it counts toward the plan keyword limit. This informs the agent of side effects and constraints without contradicting 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 sentences with zero filler. The primary action and core constraints are front-loaded, and the permissions/limit context follows naturally. Every phrase adds meaningful information.

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 simple two-parameter tool with no output schema, the description covers the essential context: who can use it, required subscription, limit impact, and character restrictions. It does not describe the return value or behavior on duplicates, but given idempotentHint and the tool's simplicity, this is adequate.

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 100%—both parameters have descriptions. The description adds the max-80-character limit (already in schema) and clarifies that country/language come from the site, which relates to parameter interpretation but does not introduce new parameter semantics. It meets the baseline for high schema coverage.

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 clear verb ('Add') and specific resource ('keywords to daily Google rank tracking for a website'), and distinguishes itself from the sibling get_keywords by implying a mutating operation. The additional constraints (max 80 characters, country/language from site) make the purpose unmistakable.

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 provides prerequisites (owners/admins only, active subscription, counts toward plan limit) but does not explicitly contrast with alternative tools like get_keywords or other mutating tools. There is no 'when to use' versus 'when not to use' guidance, though the purpose is self-evident.

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