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

Annotations declare readOnlyHint=false, idempotentHint=false and destructiveHint=false, covering safety, but the description adds the two-step upload behavior, the short-lived nature of the URL, and the important caveat that server-side filesystem paths are unreadable. That goes meaningfully 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?

Three short sentences, front-loaded with the when-to-use condition, then mechanism, then the critical constraint. No filler words; every sentence earns its place.

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 create tool with an output schema, the description covers the when, the return shape, the follow-up step, and a key constraint. It is nearly complete, though it could mention parameter expectations (e.g., that sizeBytes should match actual bytes) and that the returned URL and headers must be used verbatim. Still, it is strong.

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 0%, so the schema itself provides no per-parameter semantics. The description implies but does not document the parameters; it does not clarify fileName, contentType, sizeBytes or category meaning. Baseline 3 is appropriate given the schema carries the names but no descriptions.

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 states a specific verb+resource: it prepares a media upload and returns a short-lived PUT URL, headers and uploadIntentId. It clearly distinguishes itself from the sibling finalize_media_upload and from attach_media by making this the first step in a two-phase upload flow.

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 explicitly says 'Use when uploading a local image, video or document from any MCP client', and adds the critical exclusion 'A local filesystem path cannot be read by the server.' It also names the follow-up tool (finalize_media_upload), giving a clear sequence.

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