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

Annotations already cover read-only and closed-world safety, so the description is free to add the non-obvious constraint: the feature requires Studio plan and above, which affects whether the call returns anything useful. It omits pagination/empty-result behavior, but the plan gating is genuine 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?

A single tight sentence covers resource, return fields and the `custom:<name>` usage pattern, followed by the dashboard-upload note and plan tier. Front-loaded and waste-free, though the multi-clause opening sentence is denser than it needs to be.

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 carries the burden of describing return values and does so by naming all four fields and the reference format an agent needs to use in a style's icon-image. The plan requirement plus the dashboard-upload note closes the main operational questions for a simple list tool.

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 tool takes zero parameters, so there is nothing to disambiguate and the baseline applies. The description instead spends its words on the shape of what comes back, which is the only semantic gap for a no-arg call.

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 the concrete resource (the workspace's custom sprite icons) and enumerates what each entry carries: name, the `custom:<name>` reference used in a style's icon-image, size and served URL. That is specific enough to distinguish it from delete_sprite, though it never says 'list' explicitly and leans on the tool name to supply the verb.

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?

Implies read/usage context by telling the agent where uploading happens ('Uploading an icon is done in the dashboard'), which incidentally rules out looking for a create tool here. It gives no explicit when-to-use framing or pointer to any sibling such as delete_sprite for the opposite operation.

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