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

Annotations already declare write, non-idempotent, destructive, open-world behavior, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the no-files path returns an upload link that a .zip is POSTed to via curl, and it emphasizes that `note` is mandatory. It doesn't spell out that replace_all/delete destroy content, though the destructiveHint already flags risk.

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?

A single dense sentence that front-loads the primary guidance ("Use for images, fonts...") before the mode mechanics. It packs several ideas via colons and clauses; slightly run-on, but every clause carries information and nothing is wasted.

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?

With 5 params at full schema coverage, an output schema present, and annotations covering safety, the description supplies the one thing structured data can't: the two-mode workflow and the required note. The only gap is not surfacing the destructive replace_all/delete behavior in prose, which the destructiveHint partially covers.

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 the schema already documents every parameter including the files/delete/replace_all semantics, making 3 the baseline. The description reinforces the omit-files-means-upload-link behavior and repeats that note is required, but adds no format or constraint detail beyond the schema.

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?

It states a specific action (upload files) and enumerates the resource classes it handles: images, fonts, other binaries, batches, and whole builds. The "many files at once" framing implies a batch tool, but it never names the sibling `attach_image` it could be confused with for the single-image case, so differentiation is inferential rather than explicit.

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?

It gives clear conditions for use (images/fonts/binaries, many files, or a full Vite/Astro/Next build) and distinguishes two invocation modes: send files, or send none to receive an upload link. It stops short of naming when-not-to-use or routing to `attach_image`, so it's context-rich but not fully exclusive.

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