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

Annotations only tell the agent this is a non-read, non-idempotent, open-world write; the description adds the operation is asynchronous, discloses the differing latency paths (immediate/~24h vs queued/24-72h), and states permission (Admins only), quota (plan/trial limit), and billing (prepaid balance, free) preconditions. That is substantial behavior beyond the structured hints.

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 core action is front-loaded in the first sentence, and the two auth paths are packed into two dense sentences with no filler. Slightly telegraphic but every clause carries a distinct constraint.

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?

With no output schema, the description usefully conveys the async/queued nature and timing, plus gating prerequisites. It stops short of describing what the call returns (e.g., a queued request identifier) or how to later confirm the domain was added, which is the remaining gap for a write tool.

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?

There is a single parameter with 100% schema description coverage, so the baseline is 3. The description says 'rival domain' but adds no format guidance (subdomain, protocol, www handling), so it neither compensates for nor improves on the schema.

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 opening sentence states a specific verb and resource ('Add a rival domain to monitoring'), which clearly separates this mutating tool from the surrounding read-only get_* siblings and from list_my_tracked_brands. An agent can identify the action without opening 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?

It lays out the two invocation contexts explicitly: RivalSweeper sign-in (immediate add, company Admins only, plan/trial domain limit applies, ~24h to first data) versus Developer API keys (queued request, positive prepaid balance required, 24-72h). It does not name alternative tools or a when-not-to-use condition, so it stops short of a 5.

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