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

Annotations already declare this is a non-read-only, idempotent, non-destructive write, so the safety profile is covered. The description adds genuinely non-obvious behavioral context: the call authenticates with a plan bearer token and must not be made on the x402 payment path. It does not say what happens if the host is already covered or whether there is a host cap.

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?

Three short sentences with the critical auth constraint front-loaded, so an agent sees the payment-path rule before the action. The closing sentence about check/report/best is slightly tangential to this tool but earns its place as routing 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 two-parameter write tool whose annotations cover the safety profile and with no output schema, the description covers the action and the auth scheme adequately. It leaves open what a "covered" host means, whether token is required, and any quota or plan-membership prerequisite.

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 50%, with the host parameter well documented but token left bare. The description compensates by explaining that the token is a plan bearer token and that the x402 scheme must not be used, which is meaning the schema does not supply. It still does not clarify whether token is optional, given only host is required.

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?

"Adds one covered host to an alerts plan" gives a specific verb and resource, and the word "one" signals single-host scope versus a bulk or listing operation. It is distinguishable from watch_list/watch_remove by implication, though it never names those siblings explicitly.

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 does route the agent on payment scheme (plan bearer token, never x402) and tells it that check/report/best belong to x402 instead. However, it gives no guidance on when to use this versus watch_list or watch_remove, nor any prerequisite about needing an existing alerts plan.

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