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

Annotations indicate idempotentHint: true (calling multiple times safe) and destructiveHint: false (not destructive). The description adds the context that the upload must be 'prepared' and byte transfer completed, but does not state that validation is idempotent or clarify side effects. It doesn't contradict annotations, but also doesn't add much beyond them.

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 a single, concise sentence that gets straight to the point. It front-loads the primary action and result, with no unnecessary words.

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 single parameter, 100% schema coverage, and clear annotations, the description covers the essential context for calling this tool. It could mention the expected format of the return value (file_id), but the output schema is present and likely provides that. The prerequisite of 'prepared' is also stated.

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 input schema already has 100% coverage, including a clear description of upload_id. The tool description adds no further parameter details. Since schema coverage is high, baseline 3 is appropriate.

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 states the specific action ('Validate a prepared image upload') and the key result ('return its reusable file_id'), which is clear and concise. It doesn't name sibling tools, but the verb 'complete' distinguishes it from 'prepare' in the sibling list.

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 implies that this tool should be used after preparation and byte transfer, as indicated by 'a prepared image upload'. However, it doesn't explicitly state when not to use it or mention alternatives. The required parameter description reinforces the prerequisite.

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