Project Set Thumbnail

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

No annotations are provided, so the description carries the full burden. It explains the underlying mechanism (Scratch generates thumbnails, grey placeholder), the conditional SVG-to-raster conversion, and the default fallback to the Stage's first backdrop. It does not mention permissions or error cases, but for a simple setter this is adequate; the absence of any contradiction with annotations (none exist) keeps this from being 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?

The description is well-organized: a clear lead sentence followed by practical context and a note on the ideal resolution (480x360). Each sentence earns its place—no filler—though the explanation of Scratch's thumbnail generation could be considered slightly verbose, it is still purposeful.

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?

The description covers prerequisites (published project, rasteriser availability), the default behavior, and directs to the alternative tool. An output schema exists, so return values need not be described. Minor gaps like error handling or permissions are acceptable for a straightforward setter.

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 description coverage is 100%, so parameters are already documented. The description adds meaningful context: what happens when `file` is omitted (backdrop used) and the format constraints (SVG only with a rasteriser). This goes beyond the schema's dry field descriptions.

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 states a specific verb ('Set') and a resource ('thumbnail of a published project'), clearly distinguishing it from the sibling `project_save_to_cloud` which performs the same action automatically. The purpose is unambiguous and the tool's scope is well-defined.

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 directs the agent: 'use this tool to change it afterwards' and notes that `project_save_to_cloud` does this automatically. This makes the decision between the two tools clear, leaving no ambiguity about when to invoke this tool.

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