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

Annotations already declare the safety profile (non-destructive, non-idempotent, closed-world), so the description rightly spends its words on behavior the annotations can't convey: the PUT contract ('same Content-Type'), the 1-hour ticket expiry, and the r2Path hand-off. That is substantive operational context beyond the structured fields.

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 tight sentences, front-loaded with the purpose and the LOCAL constraint before the mechanics. Every clause carries information — no filler, no restatement of the title.

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?

With no output schema, the description correctly compensates by naming the returned fields (uploadUrl, r2Path) and the full client workflow. Combined with the schema and annotations, an agent has everything needed to call it and use the result.

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 100%, so the schema already documents filename, sizeBytes, and contentType with enum values. The description adds only the Content-Type-must-match-PUT note and the existence of uploadUrl/r2Path; baseline 3 is appropriate when the schema does the heavy lifting.

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 a specific verb and resource ('Get a presigned upload URL') and immediately scopes it to 'a LOCAL image file — the one case a URL can't cover', which cleanly separates it from upload_image_from_url. An agent can pick this tool over its sibling without opening either schema.

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 gives a clear when-to-use condition (local file, not a URL) and a downstream routing instruction ('pass the returned r2Path to a generation tool instead of imageUrl'). The alternative upload_image_from_url is implied by the URL contrast rather than named explicitly, which is the only gap.

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