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

Beyond the annotations, the description discloses the two rendering outcomes: an in-chat player where supported, and a returned link that works in any browser. That is meaningful behavioral context, especially since there is no output schema. It does not explain why readOnlyHint is false or what other state playback may touch, which keeps it below 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?

One sentence, front-loaded with the action and resource, then the source tool, then the output behavior. No redundant wording.

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 one-parameter playback tool with annotations present, the definition covers origin, rendering behavior, and the fallback link. The only remaining gap is the side-effect profile implied by readOnlyHint=false, which a caller might reasonably want spelled out.

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?

The single parameter is fully documented in the schema (100% coverage, including the id pattern and origin). The description's "from get_today_feed" only repeats what the schema already says, so it adds no new syntactic or format meaning.

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 gives a specific verb and resource ("Play a short Reulay feed video") and anchors it to the sibling that supplies the id (get_today_feed), so an agent can tell it apart from save_feed_video or browse_library. It stops short of an explicit exclusion statement, so it lands just under the top band.

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?

"from get_today_feed" establishes a clear prerequisite chain: fetch the feed first, then play an item from it. It does not name any alternative tool or state when not to use this one, but the context an agent needs to select it is present.

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