upload_file

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

With no annotations, the description carries the full behavioral burden. It does disclose two non-obvious traits: the transfer is streamed, and the local path is strictly confined to the workspace sandbox. It omits whether existing keys are overwritten, failure/partial-upload semantics, size limits, and required credentials, so the disclosure is only partial.

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?

A single compact sentence that front-loads the action and scope. Nothing is wasted, though the parenthetical is doing double duty as a constraint rather than as structure. It is appropriately sized for the content it carries.

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?

This is a mutation tool with no annotations, no output schema, and four undocumented parameters. The description covers purpose and one key guardrail but says nothing about return values, error behavior, or parameter meanings, leaving significant gaps for an agent 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 description coverage is 0% for all four parameters, so the description must compensate and largely does not. 'Local file' loosely maps to local_path and the S3 target to key/bucket, but nothing explains key format, whether bucket is optional or defaulted, or acceptable content_type values. The uncovered parameters remain opaque.

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 names a specific verb and resource: streaming upload of a local file to S3. This clearly distinguishes it from siblings like put_object_text (text payload), download_file (reverse direction), and copy_object (server-side copy). It stops short of naming those alternatives explicitly, so it stays at 4.

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?

There is no statement of when to use this tool versus put_object_text, copy_object, or download_file, and no mention of prerequisites. The parenthetical sandbox note hints that the source path must live inside the workspace, but that is a constraint rather than usage routing. An agent gets no explicit when-to-use guidance.

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