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

Annotations only say non-read-only, non-destructive, non-idempotent, non-open-world. The description adds traits the annotations cannot express: the 25 MB size limit, the 30-minute URL expiry, and the exact two-step sequence (HTTP PUT with the returned Content-Type, then import_media). This is meaningful operational context beyond structured fields.

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?

Front-loaded with the tool's role and its consumer (import_media), followed by returns, the follow-up action, and the expiry. The inline curl example is longer than strictly necessary but earns its place by removing ambiguity about the PUT step.

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?

There is no output schema, and the description compensates by naming the returned fields (uploadUrl, uploadId) and describing exactly how to consume them. Combined with the size limit, type restrictions, and expiry, an agent has everything needed to complete the two-step flow.

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 baseline is 3. The description still adds value by clarifying the allowed upload formats (PDF, PNG, JPEG, WebP) and by connecting mimeType to the Content-Type header the agent must send, plus the 25 MB constraint that the schema does not carry. It does not add per-parameter syntax 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?

States a specific verb+resource ('Start an upload of one file') and scopes it precisely to the import_media flow. It names the sibling it feeds (import_media) and the accepted file types, so an agent can distinguish it from extract_file_text or import_script without opening a schema.

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 gives the full when-and-how: call this to start an upload, then PUT the bytes to the returned uploadUrl, then call import_media with the uploadId. It also states the file-type allowance and the 25 MB cap, which are the conditions under which the tool is usable.

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