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

Annotations already declare readOnlyHint=false and destructiveHint=false, so safety is covered. The description adds valuable behavior beyond them: the file is downloaded and persisted to storage and a url is returned, plus the exactly-one source constraint. It stops short of explaining auth needs or the non-idempotent consequence of re-uploading.

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?

Three dense, front-loaded sentences: purpose, then how to call, then the downstream integration step. Every clause carries information (including the return value), with no filler.

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 mutation tool with no output schema, the description compensates by stating the return value (url saved to storage) and the follow-up integration. Combined with full annotation and schema coverage, an agent has enough to call it correctly; only sibling differentiation 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%, so the baseline is 3 and the schema already documents each field. The description adds a constraint not encoded in the schema — that url and file_base64 are mutually exclusive ('ровно один') — which is genuinely useful disambiguation.

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 names a specific verb+resource (upload media — image/video/audio) and scopes it to the multimedia block of any widget, which is more precise than the title. It does not, however, distinguish itself from the very similar sibling upload_quiz_widget_image, leaving the agent to infer which image-upload path applies.

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 provides clear workflow context: pass type plus exactly one of url/file_base64, then substitute the returned url into update_quiz_widgets (multimedia.imgUrl/videoUrl/audioUrl). That tells the agent when the tool sits in a flow, but it offers no explicit exclusion against the similar upload_quiz_widget_image sibling.

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