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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds genuinely useful context beyond that: the empty-facet failure mode for unprocessed responses and the fact that data is scoped to a single session recording. It does not need to describe return format since an output schema exists.

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?

Front-loads the resource definition, then the key, then the edge-case behavior, which is the right order. The facet catalogue in the first sentence is somewhat long and duplicates what the output schema already documents, but it is informative rather than 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?

With an output schema present, the description need not explain return shape, yet it still covers the lookup key source and the coverage limitation that would otherwise cause an agent to misread empty results as a bug. Nothing required for correct invocation is missing.

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?

Single parameter with 100% schema description coverage, so the schema already documents insightId. The description restates the same sourcing guidance ('from responses_search / recent_responses / response_detail') without adding syntax or format constraints beyond the schema.

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?

Names the specific resource (video-derived UX signals from one usability-test recording) and enumerates the five facet families returned (findings, frictions, task performance, emotional moments, mental-model gaps) with enough detail to distinguish it from siblings. The lookup key (insightId) and its sources are stated, so an agent knows exactly what this returns and how to key it.

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 precondition: only usability-test responses whose recording was processed by video-metadata extraction have data, and other responses return empty facets — an explicit when-not signal. It also points to the sibling tools that supply the insightId (responses_search / recent_responses / response_detail). It stops short of naming an alternative tool for agents who want non-video response data.

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