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

Annotations already declare non-readOnly, non-destructive, idempotent, closed-world behavior. The description adds genuinely useful context beyond that: the tool itself does not transfer bytes, an external HTTP upload must happen between create and complete. It omits slot expiry, size limits, and failure/recovery behavior, so it is helpful but partial.

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: what it does, how the flow proceeds, and what it is not. The workflow ordering is front-loaded and every sentence carries 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?

An output schema exists, so the returned upload URL need not be described, and the two-phase flow is otherwise clear. The remaining gap is input-side: no guidance on the file parameters or on constraints like the 1 GB cap and slot lifetime.

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 25%, so the description should compensate, but it says nothing about fileName, mimeType, or sizeBytes — including the 1 GB ceiling. Only idempotencyKey is explained, and that explanation lives in the schema, not the description.

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 and resource ('Creates an upload slot') and clarifies the two-step protocol that follows. The closing sentence ('does not import a ChatGPT attachment or an arbitrary URL') scopes it away from import-style siblings like dub_import_file, though it never names a sibling directly.

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?

Gives clear context: use this first, then POST bytes to the returned URL, then complete it — which implicitly routes the agent to dub_complete_upload. It also gives an exclusion (no attachments/arbitrary URLs). It stops short of naming the exact alternative tools or when to poll status instead.

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