Upload file part

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

The annotation openWorldHint is minimal and doesn't convey safety or side effects. The description adds a useful behavioral detail: 'Body is base64-encoded bytes.' However, it omits other operational traits like error handling, idempotency, or single-use URL behavior, leaving some gaps. It doesn't contradict annotations.

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 concise sentences, front-loaded with the action and key requirement. Every word earns its place with no redundancy.

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 simple two-parameter tool with no output schema, the description adequately covers the core usage and correctly places it within the create-session upload flow. It could mention that multiple chunks may be required, but it's sufficient for an agent to select and 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% with descriptions for both parameters. The tool description largely restates schema info ('absolute upload URL from the session', 'base64-encoded bytes') without adding new semantic meaning. This meets the baseline for well-documented schemas.

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 uses a specific verb 'Upload' and clearly identifies the resource: 'a chunk to an absolute upload URL returned by create session.' This distinguishes it from sibling file tools like files_create_session or files_delete, making its role unambiguous.

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 explicitly references 'create session', indicating this tool is used after session creation. It provides clear context for when to invoke it, though it doesn't explicitly exclude alternatives or mention when not to use it. This matches the 'clear context, no exclusions' level.

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