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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description's real addition is the auth constraint ('Plan bearer token, never x402'), which is valuable context an agent would otherwise get wrong, plus a partial field list; however it says nothing about pagination, the limit behavior, or error cases on a read tool with a required time parameter.

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 compact sentences with no filler, and the schema-dependent facts (ISO time, plan scoping) come early. The opening auth fragment is terse to the point of being cryptic, but nothing 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?

With no output schema, the description does partial duty by naming the price_differs_from_listing payload fields. Still missing for a four-parameter, no-output-schema tool: what limit does, whether results are paginated or capped, and the overall response envelope.

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 25% (only host is described), so the description must compensate. It does clarify that since is an ISO time, that token must be a plan bearer token rather than x402, and that host is meaningful mainly on data plans — but limit is entirely undocumented in both schema and description, leaving one of four parameters opaque.

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 ('Change events since an ISO time') and goes further by scoping results by plan type: all hosts on an alerts plan vs. one host on a data plan. An agent can distinguish this from siblings like history or check only by inference, but the core purpose is unambiguous.

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 plan-dependent scoping ('hosts on an alerts plan, or for one host on a data plan') implies when this tool applies versus other polling tools, but there is no explicit statement of when to prefer it over history, check, or receipt_verify, and no mention of prerequisites beyond the token type.

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