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

Annotations are minimal (readOnlyHint=false, destructiveHint=false), so the description carries most of the burden. It adds 'App-only' and 'resume-safe', hinting at authentication context and repeatability, but does not explain URL validity, required permissions, or side effects. It neither contradicts the annotations nor fully discloses behavior.

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 one short sentence that front-loads the core action, resource, and scope. Every word contributes meaning; there is no redundant or filler content.

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?

All four required parameters are fully documented in the schema, but there is no output schema and the description does not explain how the returned URLs fit into the broader multipart flow (e.g., uploading parts to R2 and then calling mcp_confirm_upload). The tool is understandable for a single call, but some workflow context is left implicit.

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%, and each parameter already has a clear description (e.g., 'from prepare'). The description's phrase 'one or more multipart upload parts' and 'resume-safe' adds slight framing, but no additional parameter-level meaning beyond what the schema provides.

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 ('return') and resource ('presigned R2 URLs for one or more multipart upload parts'), making the tool's action clear. It does not explicitly contrast with sibling tools like mcp_prepare_upload or mcp_confirm_upload, but the multipart part-signing scope is distinct enough.

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 provides context ('App-only', 'resume-safe') that implies when the tool should be used, but it does not explicitly state when to use this tool versus siblings such as mcp_prepare_upload, mcp_confirm_upload, or upload_interview. No exclusions or alternative routing are given.

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