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

Annotations are sparse and only indicate readOnly/idempotent/destructive hints, so the description carries the behavioral burden. It discloses the upload_url expiry, deletion policy, unused-upload quota, file size limit, supported formats, and cost, which is rich and useful behavior beyond what annotations provide.

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 compact yet information-dense, with the primary purpose and sibling relationship front-loaded before operational details. Every sentence adds a distinct piece of information: purpose, return values, format/size, expiry/lifecycle, quota, cost, and alternative path.

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?

An output schema exists so return values need not be elaborated. The description covers the full lifecycle, constraints, alternatives, and edge cases, making the tool callable without additional investigation. Nothing essential 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?

Schema coverage is 100% and both parameters already have clear descriptions and an enum for content_type. The description adds useful context like the 10 MB limit and the fact that file_name becomes the hosted file name, but this is mostly reinforcing rather than deeply extending the schema semantics.

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 and resource: it 'prepares the upload of an image file' and explicitly connects it to set_article_cover_image and upload_article_image. It clearly distinguishes when this tool is needed versus when it is not, which separates it from sibling tools.

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 explicit when-to-use guidance: use it when an image has no public URL and you need to pass it to set_article_cover_image or upload_article_image. It also names the alternative explicitly ('pass image_url directly') when a URL already exists, so an agent knows exactly when to avoid this tool.

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