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

The description adds valuable behavioral details beyond the annotations: the presigned URL nature, the required PUT step, the 1-hour expiration, and the r2Path output. It does not contradict the readOnlyHint=false (write operation) and destructiveHint=false. Minor gap: no explicit mention of response structure beyond uploadUrl and r2Path, but these are named.

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?

Three sentences, tightly packed with essential information. No filler or repetition. The purpose is front-loaded, and each sentence earns its place by explaining workflow and constraints.

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?

The tool is simple, and the description covers the critical workflow, output, and expiration. With no output schema, it names the returned fields (uploadUrl, r2Path). It could mention error cases or security notes, but for a presigned upload tool, this is sufficiently complete.

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 baseline is 3. The description does not add meaning beyond the schema for parameters like filename or sizeBytes; it only references contentType in the PUT step. However, it does clarify the role of uploadUrl and r2Path as outputs, which is helpful, but that's not parameter semantics.

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 clearly states the tool's function: 'Get a presigned upload URL for a LOCAL image file'. It uses a specific verb ('Get') and resource ('presigned upload URL'), and explicitly differentiates from URL-based uploads with 'the one case a URL can't cover'.

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 provides explicit usage instructions: PUT to uploadUrl with the same Content-Type, then pass r2Path to a generation tool. It also notes the 1-hour expiry, giving clear context for when and how to use the tool. The distinction from URL uploads implicitly guides tool selection.

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