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

Beyond the annotations (readOnly=false, idempotent=false), it discloses material behavior: the link is short-lived, each PUT carries at most 95 MB, larger files must be chunked in order via ?offset, each response returns `next_offset`, and offset 0 overwrites prior content. This is exactly the kind of operational context an agent cannot get from the annotations alone.

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 core purpose is front-loaded in the first clause and the body is dense but readable. The trailing 'Requires: token + live sandbox_id. ≤95 MB per PUT; use ?offset for more.' restates content already established, which is a minor redundancy and the only thing keeping this from a 5.

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?

For a chunked-upload tool with no output schema, the description covers TTL, size limits, offset chaining, and the `next_offset` field well. It stops short of describing the rest of the returned payload (e.g. the URL field name or link expiry), but an agent has enough to call it 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?

Schema coverage is 100%, so the baseline is 3, but the description reinforces max_bytes ('up to 2 GB') and adds semantics not present in the schema, notably the overwrite-at-offset-0 behavior on `path` and the chunked-upload offset mechanic that governs how the returned URL is used.

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 gives a specific verb and resource: returning a short-lived HTTPS link to PUT one file into a sandbox at `path`. The 'ONE file'/'up to 2 GB' scoping and the 'No base64 through this conversation' remark implicitly route the agent away from upload_file, but no sibling is named, so differentiation is inferential rather than explicit.

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 the prerequisites ('Requires: token + live sandbox_id') and the operative workflow (one PUT ≤95 MB, chunked PUTs via ?offset for larger files). What is missing is an explicit 'use this instead of upload_file/get_download_url when…' condition, leaving the alternative-selection rule to be inferred.

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