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

With no annotations, the description carries the full burden, and it only partially does so: it discloses the return shape (side-by-side image plus changed-region pixel boxes in source coordinates), which is genuinely useful. It says nothing about whether this is read-only, whether it captures new frames or reads stored ones, or cost/latency for a visual operation.

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 front-loaded sentence with no filler; the output description is packed efficiently into the same line. Brevity is appropriate, though the terse phrasing contributes to the ambiguity noted elsewhere.

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?

Three required parameters at 0% schema coverage, no annotations, and no output schema mean the description should be doing much more. Describing the return value helps, but the missing parameter formats and safety profile leave an agent unable to call this correctly without guessing.

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 0% across three required params, so the description must compensate and largely doesn't. "Two moments" loosely maps to a and b, but their format (timestamp, frame ID, image reference?) is never stated, and watch_id is entirely unexplained.

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 verb and resource ("Compare two moments") and even describes the output shape (side-by-side plus highlighted pixel boxes). However, "moments" is undefined and nothing distinguishes this from siblings like frame, look, or image, so an agent can't confidently pick it over those.

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?

No when-to-use or when-not-to-use guidance, and no mention of alternatives such as frame or look. The verb "compare" implies intent but the agent must infer the scenario and prerequisites entirely.

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