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

Goes well beyond the annotations by disclosing that the URL is single-use and expires in 15 minutes, that bytes never pass through the model, that the image is resized server-side like upload_image, and by giving the exact follow-up PUT invocation. The annotations only declare non-read-only/non-idempotent; the description supplies the real operational behavior.

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?

Front-loads purpose and the base64 rationale, then layers the return shape and the concrete curl step. The embedded command is long but earns its place for a multi-step tool; a couple of clauses could be tightened.

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?

No output schema exists, yet the description documents both the returned object ({ uploadUrl, method, contentType, expiresInSeconds, howTo }) and the follow-up PUT response ({ url }). Nothing an agent needs to complete the flow is missing.

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, but the description adds the conditional coupling between slot and its target id (slot "avatar" + entryId, or slot "scene" + scenarioId) and notes filename sets the image type. That pairing guidance is useful beyond the per-field schema text, though it partly echoes it.

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?

States a specific verb+resource (get a one-time signed URL to upload a local image file) and explicitly distinguishes itself from the sibling upload_image by framing itself as the base64-overflow alternative. An agent can tell which tool to reach for 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?

Gives an explicit when-to-use ('the fix for files too big to inline as base64', local files), names the sibling it parallels (upload_image), and states an exclusion ('the scenario COVER is editor-only and cannot be uploaded here'). Routing conditions are fully spelled out.

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