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

Annotations already cover the safety profile (read-only, idempotent, non-destructive, closed-world). The description adds genuinely useful behavior beyond that: the output is counts only, it does not enumerate TLDs, and it tracks a bounded TLD set rather than all TLDs. That scope and output-shape disclosure is the kind of context annotations cannot convey.

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 tight paragraphs, front-loaded with the core behavior and scoping, followed by the routing line. Every sentence carries information and none is wasted.

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?

An output schema exists, so return formatting need not be explained, yet the description still clarifies that counts (not lists) are returned. Combined with annotations covering safety, nothing an agent needs to select and call this tool is missing.

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% and the single 'keywords' param already documents itself with the max-50 constraint. The description adds the exact-match semantics (each name is evaluated as keyword.tld), which is meaningful, but otherwise restates the schema. Baseline 3 is appropriate.

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?

States a specific verb and resource: count how many TLDs each exact name is registered in, with the scope ('among the TLDs DomainKits tracks') and the breakdown (popular/country-code/other gTLDs). It also names the sibling tools it is not (tld_check, bulk_available), so it is distinguishable without opening any 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 'Related' line routes the agent well: tld_check for per-TLD status on one keyword and bulk_available for specific domain status, plus the 'does not list individual TLDs, check availability, or report sale status' exclusions. It stops short of an explicit 'use this when you want aggregate counts across keywords' trigger, but the context is clear.

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