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

With no annotations, the description carries the burden of explaining side effects. It states it 'returns a presigned PUT URL' which is a behavior, and implies the actual upload happens later via finalize_upload, so it does not create or modify permanent records directly. However, it omits details like URL expiration, authentication requirements, or whether any server-side state is created. This is acceptable for a simple operation but not fully transparent.

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 two sentences, direct, and free of redundant or irrelevant information. It front-loads the core purpose (presigned PUT URL) and immediately follows with the next step, making it efficient and scannable for an agent.

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?

Lacking an output schema, the description does not need to explain return values, but it does indicate the next operation (finalize_upload). It covers the key workflow steps, though it omits potential error cases, upload limits, or how the URL should be used (e.g., HTTP method, headers). For a simple two-step flow, it is reasonably complete.

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?

The schema has no descriptions for parameters, and the description only partially explains them. It connects 'filename' to .glb and 'withPreview' to optional PNG preview, but 'contentLength' is entirely unexplained—what it represents, why it's required, and how it's used remain ambiguous. Given the low schema coverage, the description should provide more detail but does not.

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 the tool returns a presigned PUT URL for a .glb file with an optional PNG preview, which is a specific and distinct action. It names the exact resource type and even names the next step (finalize_upload), making its purpose unambiguous relative to sibling tools like submit_asset_from_url or finalize_upload.

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 explicit guidance by saying 'For clients that can upload bytes' and instructs to call finalize_upload after, which tells the agent when to use this tool and what to do next. It does not explicitly mention alternatives (like submit_asset_from_url), but the condition 'can upload bytes' effectively distinguishes it from URL-based uploads.

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