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

Annotations already declare readOnlyHint/openWorldHint/idempotentHint/destructiveHint, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the fact that the caller must issue a PUT to the returned upload_url and that cdn_url is the post-upload access path. It omits signed-URL expiry and permission requirements, keeping it from 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?

Front-loaded with the core action and consumption workflow before the Args listing, so a reader gets the essential contract in the first sentence. Every sentence earns its place; the Args block is standard but slightly verbose.

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?

Output schema exists, so return-value explanation is not required, yet the description still usefully names upload_url and cdn_url. Parameters are covered. For completeness it could mention signed-URL lifetime and whether the files array creates assets up front, but an agent can invoke this correctly as written.

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 0%, so the description carries the burden, and it largely does: it documents all three parameters and crucially clarifies that files is a JSON array of filenames (with an example like ["images/photo.jpg", "doc.pdf"]) despite the schema typing it as a plain string. folder's "prefix" semantics are stated. project_id is documented only tautologically ("The project ID").

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 ("Get signed upload URLs for one or more files") and goes further by explaining the two-step upload workflow. It is immediately clear what the tool returns and how to consume it. It does not explicitly distinguish itself from the close sibling get_attachment_upload_url, so it stops short of a 5.

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 solid guidance on how to USE the result (PUT to upload_url, then read cdn_url), which is real usage context. However, it never says when to pick this tool over the sibling get_attachment_upload_url or get_asset, nor any prerequisites. Usage is implied rather than routed.

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