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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint), so the bar is context-adding. The description adds one genuinely useful behavioral fact — retired effects still appear in the list and are refused at submit at no cost — but omits ordering, pagination, or why some entries lack modes beyond a guess ('likely').

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 dense sentences plus the raw endpoint; the scope statement leads and the retired-effect caveat follows. Some phrasing is clipped to the point of ambiguity ('takes a prompt', 'the modes each allows'), which costs a little clarity but not much length.

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 correctly carries the return-value burden by listing the fields an agent will receive and flagging the retired-effect edge case. It does not describe the response envelope or whether results are paginated, which is the main remaining incompleteness for a paginated-looking list endpoint.

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 description coverage is 100% for the single email parameter, so the schema fully documents it and the description adds nothing about it. Baseline 3 applies when the schema does the heavy lifting, which is the case here.

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 names a specific resource (Kling's video effects) and explicitly ties it to the consumer tool kling_effect_video, so an agent can place it in the workflow without opening a schema. It also enumerates the meaningful fields returned (name, caption, modes, hot, prompt support). The only gap is that no verb is stated in the description itself — 'list' comes from the name/title pair, not the prose.

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?

By naming kling_effect_video as the consumer, it implicitly tells the agent to call this first to discover valid effect names and modes. It also supplies practical guidance for interpreting results ('no modes listed is likely retired'). It stops short of an explicit when-not-to-use condition, but no sibling competes for this role.

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