generate_asset_thumbnail

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

Annotations already declare the safety profile (readOnlyHint=false, idempotentHint=false, destructiveHint=false), so the bar is lower, and the description adds real context: it discloses that a fresh thumbnail is written into the package thumbnail map (a mutation, consistent with the annotations) and that when rendering is unavailable it degrades to reporting cached state. It omits the cost/latency of forcing a render, which is the main remaining unknown.

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 core action, then conditions and finally the return shape. The Returns block is doing necessary work because there is no output schema. Minor filler in phrasing ('honestly reports') but no wasted sentences.

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 render-and-cache tool with no output schema, the description supplies the full return structure inline and explains both branches of behavior, including the honest-report fallback so a caller does not mistakenly assume a thumbnail is always produced. Nothing needed to call it correctly 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 coverage and an inline description ('Object path or package path of the asset'), so the schema already carries the semantics. The description adds nothing about path format beyond what the schema provides, making the baseline 3 appropriate.

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 pair (render and cache) on a specific resource (asset thumbnail), and adds the fallback behavior 'or report the existing cached one'. This distinguishes it from the sibling get_asset_thumbnail, which only reads.

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?

The description explains the two execution modes (rendering available vs unavailable), which is conditional behavior rather than guidance on when to pick this over a read-only sibling. It never names get_asset_thumbnail or states a 'use this when' condition, so usage must be inferred.

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