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

With annotations covering safety (readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=true), the description still adds real behavioral context: it is an asynchronous job, output duration equals the motion video length, and it carries per-second credit pricing (9 credits/s std, 35 per 5s for kling-v2-6). Cost and job semantics are not in the structured fields, so this is meaningful added value.

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?

Dense and front-loaded: purpose first, then input provenance, then cost, then job nature and endpoint. Every sentence carries information. Slightly cryptic parentheticals keep it from a perfect score, but there is no filler.

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 9-parameter, no-output-schema tool, the description supplies the missing return shape (a job/task, like kling_text_to_video), duration behavior, and cost. Combined with full schema coverage, an agent has enough to call it correctly; only the explicit sibling differentiation is absent.

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%, so the baseline is 3, but the description adds semantics the schema lacks: the 3-30s bound and provenance for motionUrl, and the model_name credit differential. These go beyond the enum/type documentation, lifting it above baseline.

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: 'make the person in imageUrl perform the movement of motionUrl'. The core operation is unambiguous and the 3-30s constraint is given. It does not, however, distinguish itself from the closest siblings (kling_image_to_video, kling_avatar_video, kling_lipsync), so an agent must infer the difference from the inputs.

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 tells the agent where motionUrl comes from (kling_upload_asset or kling_list_motions) and that the result is an async job 'like kling_text_to_video', which is useful prerequisite/routing context. But there is no explicit when-to-use-this-vs-alternatives guidance and no exclusions, so usage is implied rather than stated.

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