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

Annotations already declare readOnly, idempotent, non-destructive and closed-world. The description adds real behavior beyond that: the four-asset cap, that images come back as image content while other types return metadata only, and the MCP Apps gallery rendering. That is meaningful return-behavior context the annotations cannot carry.

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?

Roughly two sentences, front-loaded with purpose and scope, followed by the fallback routing. Every clause carries information; nothing is redundant.

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 no output schema, the description carries the burden and does describe what comes back per asset type, which is the key gap for a preview tool. It omits edge cases such as behavior when an asset is missing or oversized, so it is strong but not exhaustive.

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 only 50%, with assetIds carrying no inline description, but the description compensates by stating 'up to four stored assets from one workspace', which explains both the maxItems=4 bound on assetIds and the single-workspace constraint on workspaceId. It adds material meaning over the bare array/string 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?

States a specific verb and resource ('Returns compact previews of up to four stored assets'), plus the scope constraint of a single workspace. It also distinguishes itself from sibling fuzz_download_asset, which serves originals, so an agent can route correctly without opening any schema.

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?

Explicitly routes the agent to fuzz_download_asset when original files are needed, which is a clear alternative with a selecting condition. It does not spell out an explicit 'do not use this when...' case, but the preview-vs-original split is clear enough.

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