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

Beyond the annotations, the description discloses key behavior: the URL is expiring and authorized, and the tool only creates a handle rather than performing the upload itself. It also lists allowed extensions. Annotations already indicate non-read-only, but the description adds meaningful context about the expiring URL and the purpose-specific flow.

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 concise and front-loaded with the core behavior. The font explanation is a bit lengthy but earns its place by clarifying a non-obvious workflow. No redundant filler; each sentence contributes distinct information.

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?

Given an output schema exists (covering return values) and annotations convey the mutation nature, the description covers the essential behavior: creating an expiring PUT URL, allowed extensions, and the font-specific flow. It doesn't mention the subsequent upload_complete step, but that is a workflow detail arguably outside this tool's own description. Overall, it is complete enough for correct invocation.

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 parameters are already documented. The description adds semantic value by explaining the purpose=font workflow and explicitly tying it to asset_import, which goes beyond the enum descriptions. It also relates allowed extensions to filename, reinforcing the schema's 'supported extension' note.

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 'Create a direct upload handle' — a specific verb, resource, and target. It also describes the output ('expiring authorized PUT URL'), which distinguishes it from siblings like upload_complete and asset_import. The allowed extensions list further scopes the tool's purpose.

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?

Provides a clear workflow for fonts ('Use purpose=font for a typeface, then asset_import it') and implies general use cases for other asset types. It doesn't explicitly list when not to use this tool or name alternatives, but the context is clear enough for an agent to select it appropriately.

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