upload_skill_image

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

With no annotations provided, the description carries the full burden. It adds a key safety trait ('No generation is started') and the instruction to use 'actual accessible bytes/URLs only,' which helps agents avoid invalid inputs. It does not disclose storage, lifetime, permissions, or other side effects of preparing the image, so transparency is only partial.

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?

Three sentences with the core purpose and return value front-loaded, followed by concise caveats about real inputs and no generation. The direct-passing note is slightly ambiguous but not padding, and the overall length is appropriate.

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 definition covers the essential contract: it returns imageUrl, does not start generation, and requires real accessible bytes/URLs. However, without an output schema or annotations, it leaves the purpose/upscale distinction and the exact relationship to direct generation partly ambiguous, so an agent may still need to infer important call context.

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 baseline 3 applies. The description reinforces the no-fabrication rule and notes that external URLs/local paths can bypass the tool, but it adds little new meaning about purpose, sourceUrl, or imageBase64 beyond what the property descriptions already provide.

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 concrete outcome ('Prepare a reference image and return imageUrl') and explicitly distinguishes the tool from generation by adding 'No generation is started.' The verb 'prepare' is slightly vague, but the tool name, the return-value mention, and the sibling context make the resource and result reasonably clear.

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 gives partial routing guidance by noting that external URLs and local file paths 'can also be passed directly to the generation skill' and by warning against fabricated inputs. However, it never clearly states when upload_skill_image is required versus when to skip it, and the sourceUrl parameter makes the 'external URLs can be passed directly' advice ambiguous.

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