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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds value beyond them by disclosing cost ('Free') and describing the return payload (crops with positions), which is behavioral context the annotations do not carry.

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?

A single compact sentence front-loads the action, then folds in the return shape, the use case, the cost and the endpoint with no filler. Every clause earns its place.

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 compensates by stating what comes back (crops and positions), and it names the endpoint and cost. It does not cover failure modes (e.g. no face detected, fetch failure), which for a two-parameter read tool is a minor remaining gap.

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%: the schema already documents that imageReference is a public https URL best sourced from kling_upload_asset and that email is needed for multi-account tokens. The description adds no parameter-level detail beyond that, so the baseline 3 applies.

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 ('Find the faces in an image') and goes further by naming what is returned (crop and position) plus the concrete downstream use case (picking faceNo for kling_kolors_image). An agent can distinguish it from siblings like kling_kolors_image without opening either 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?

Gives a clear motivating scenario ('e.g. to pick faceNo for kling_kolors_image reference face'), which tells the agent when this tool is the right precursor step. It stops short of explicit when-not conditions or naming alternatives for other face/identity workflows, so it is not a 5.

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