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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered; the description adds real value by describing the payload (metadata, optional preview image, structuredContent) in the absence of an output schema. It also explains pack semantics — listing_kind=pack means N separate artboards, not an animation — which is behavioral context no annotation carries.

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?

The retrieval purpose and return contents are front-loaded in the opening sentence, and the pack/artboard clarification earns its place. The closing sentence about subscribers dragging items onto their canvas is product color rather than invocation guidance and is the one part that could be cut.

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 read tool with no output schema, the description covers what is returned and how to interpret pack-type results, which is the main ambiguity an agent would face. What remains thin is any note on error behavior for an invalid or non-existent id.

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?

There is a single uuid parameter at 100% schema coverage, and the schema already states it comes from list_marketplace_assets. The description's "by id" adds nothing 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?

The first sentence gives a specific verb and resource ("Fetch one asset library item by id") and enumerates what comes back (metadata, optional preview image, structuredContent), which separates it from the sibling list_marketplace_assets. An agent can tell immediately that this is a single-item retrieval, not a listing.

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?

"Use after list_marketplace_assets" gives a clear sequencing rule and the schema reinforces that the id comes from the list call. There is no explicit when-not guidance or comparison against the sibling get_asset, so the routing is clear in one direction only.

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