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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), and the description adds real behavioral detail beyond them: results are playable cards, and there is a documented fallback to the user's weakest mindset from the assessment when the feeling doesn't match. That fallback is exactly the kind of hidden behavior an agent needs to know; only the absence of any volume/result-count expectation keeps it from a 5.

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-loaded with the core action, then a long but functional enumeration of use cases, then the input example and the fallback rule. The situation list is lengthy and could be trimmed, but each clause is distinct and helps matching rather than padding.

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 two-parameter read-only recommender with no output schema, the description covers the trigger conditions, the natural-language input style, the shape of the result ('playable cards') and the fallback path. Only the timing/duration parameter and what happens if nothing matches at all are left unaddressed.

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 100%, so the baseline is 3, but the description earns more by instructing 'Pass their words' with verbatim examples ('anxious before a board meeting', 'can't focus'), clarifying that no taxonomy or keyword mapping is expected. It never mentions maxMinutes, leaving that one parameter to the schema alone.

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 opens with a specific verb+resource: 'Pick the best short Reulay video experiences ... shown as playable cards.' It makes clear this recommends rather than plays, which distinguishes it from siblings like start_experience and browse_library, and it states the input basis ('how the user feels right now').

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 gives a rich set of concrete triggering situations (stress, pre-meeting nerves, burnout, aftermath of a hard conversation, trouble sleeping) that map directly onto when to call it. It stops short of naming alternatives or exclusions — e.g. when to use browse_library or start_experience instead — so it is clear context without routing rules.

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