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

Annotations already cover safety hints, but the description adds valuable operational behavior beyond them: returned fields (uploadId, key, fileName, parts), the requirement to PUT each piece within an hour and retain each ETag, and per-server/per-account storage caps. These details are essential for correctly completing a multipart upload workflow.

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 front-loaded with the key prerequisite, then describes the operation and return values, and finally lists the workflow alternatives. Despite being dense, every sentence carries relevant information for selecting and invoking the tool.

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 the lack of an output schema, the description still explains what the call returns and how to proceed with the returned parts. It covers file-type constraints, size limits, part upload behavior, and sibling tools for completion, inspection, and aborting, which is complete enough for an agent to call this complex multipart upload tool correctly.

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 itself contains descriptions for fileName, fileSize, partCount, and serverId, but the tool description adds only partial semantic context: file type restrictions, the 512 MiB cap, and the need to PUT each part. It does not clarify the relationship between fileSize and partCount or explain the required serverId path parameter, so it does not fully compensate for the reported low schema coverage.

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 opens with a specific verb and resource: it 'Begins uploading one .jar or .zip mod, plugin, datapack or resource pack'. It also distinguishes the tool from its sibling workflow tools by naming completeAssetUploads, inspectAssetUpload, and abortAssetUploads.

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?

It states a clear precondition ('Only for an assistant that can send the user's file with HTTP PUT, such as a coding agent with a shell') and then maps the follow-up path: completeAssetUploads installs, inspectAssetUpload checks, abortAssetUploads discards. This gives an agent explicit when-to-use and next-step guidance.

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