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

Annotations already declare readOnlyHint=false, destructiveHint=true and openWorldHint=false, so the write profile is covered. The description adds real behavioral value by disclosing the ~10MB size ceiling and why base64-over-JSON is unsuited to large files, though it never says whether an upload overwrites an existing object at the same key — the key destructive detail given destructiveHint=true.

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?

Two sentences, purpose front-loaded, with the constraint and the alternatives packed into the second without wasted words. No repetition of schema or annotation 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?

For a write tool with annotations covering safety and no output schema, the description covers the key operational constraint and escape hatches. The remaining gap is overwrite/conflict semantics on an existing key, which an agent would want before calling a destructive upload.

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 75%, with key, contentType and contentBase64 documented in-schema and only bucketId bare. The description reinforces the meaning of contentBase64 (base64-over-JSON) but adds no syntax, encoding, or size-per-call detail beyond the schema, so baseline 3 applies.

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 ("Upload a file to a bucket") plus the transfer mechanism ("from base64-encoded content"), which cleanly separates it from file_download, file_delete, and files_list among the bucket siblings.

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 an explicit when-not boundary (~10MB decoded) and names two concrete alternatives — the CLI (`nexus bucket upload`) and the streaming PUT endpoint — so the agent knows exactly when to route elsewhere. Nothing is left to inference.

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