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

Annotations already declare readOnly=false, destructive=false, idempotent=false, and openWorld=true. The description adds valuable behavioral constraints beyond annotations, including plan restrictions and a ~3MB cap for dataBase64.

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?

It is front-loaded and dense with useful detail, with no obvious filler. Some phrasing is cryptic, such as the parenthetical about provider and videoId, but overall it earns its space.

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 input routing and constraints well, but with no output schema it does not explain return values like mediaId or public URL. It also does not resolve the relationship with the sibling upload_image tool.

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%, so the baseline is 3. The description adds meaning by explaining routing rules, when to use fileUrl, and that dataBase64 is a last resort with mimeType needed for non-images.

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 clearly states the verb and resource: upload any plan-allowed file, with detailed routing by media type. It does not explicitly differentiate from the sibling upload_image tool, which is a meaningful gap given that both can handle images.

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 useful context for input choice, such as images going to CDN, video/audio/pdf/zip going to R2, and dataBase64 being a last resort. However, it does not say when to use this tool versus alternatives like upload_image or when not to use it.

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