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

The annotations already establish that this is a non-read-only, non-idempotent mutation, and the description adds the key side effect: the returned upload id is single-use and consumed by the first create or update that attaches it. A small gap is that the description doesn't explicitly mention the outbound fetch triggered by source_url, though the schema already documents that.

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 with no filler. The core purpose and output are front-loaded, the alternative is offered next, and the format/lifecycle constraints follow.

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 required fields and no output schema, the description supplies what's needed: the output, how to use it, the alternative path, allowed formats, and the single-use consumption behavior. Nothing essential to calling it correctly 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 description coverage is 100%, so the schema already documents source_url and image_base64, including their mutual exclusivity and the no-data-prefix rule. The description adds usage context about the returned id but no additional meaning about the two input parameters themselves; 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 names the action and resource specifically—'upload an image for use on the SplitPage'—and states the exact output: a single-use upload id to pass as image_upload_id. It also distinguishes itself from split_set_collection_image, so an agent can tell the tools apart without reading their schemas.

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 an explicit use case: upload first, then attach the id when creating a collection. It also names the alternative for changing an existing collection's image in one step, and adds acceptance constraints (PNG and JPEG only).

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