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

Annotations provide no safety hints (readOnlyHint=false, destructiveHint=false), so the description carries the burden. It discloses allowed formats, size limit, and the return of a public_url, which are key behavioral traits. It does not mention error handling (e.g., invalid URL, size exceeded) but for a simple upload tool, these are acceptable gaps. The description adds meaningful constraints beyond the annotations.

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 two sentences, front-loaded with the core action and purpose, followed by constraints and return value. Every sentence contributes useful information with no redundancy or filler. It is perfectly sized for the tool's simplicity.

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?

For a tool with three parameters (one required), no output schema, and simple behavior, the description covers the essential aspects: purpose, accepted formats, size limit, and return value. It does not mention potential failure modes or lifecycle of the uploaded file, but these are minor for an upload utility. Overall, an agent has enough to call it correctly.

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?

The schema already covers all parameters with descriptions (100% coverage), so baseline is 3. The description adds value by specifying allowed file types and the 25 MB limit, which directly constrain the 'url' parameter. It also clarifies the default for 'file_type' (image) implicitly via the mention of allowed types. This enriches parameter understanding 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?

The description clearly states the tool's action (upload), the resource (image or video), the source (public URL), and the intended use (question text or answer image). It also lists allowed formats and size limit, distinguishing it from any generic upload utility. There is no ambiguity about what it does.

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 provides context for when to use it ('to use in question text or as an answer image'), which implicitly indicates it's for media that will be referenced elsewhere. Since there is no sibling upload tool, no alternative comparison is needed, but it could be more explicit about not using it for other media purposes (e.g., profile pictures). Still, the purpose is clear and self-contained.

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