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

Annotations already declare readOnly/idempotent/non-destructive, so 'changes nothing' largely restates them; however, 'Free' adds billing context not captured by any annotation, and the enumeration of what the listing contains (Arrakis images with SSH/banner/tools, account-saved images, download sizes) tells the agent what it will actually see. No pagination or ordering behavior is disclosed, but with zero parameters that is a minor gap.

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 front-loaded sentence identifies the resource immediately, then qualifies it. It is dense with nested parentheses (image contents, image-source split), which slightly hurts scannability, but no sentence is wasted.

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 input parameters and no output schema, the description carries the burden of describing the return set and does so: two image categories plus download size. It omits any field-level detail (IDs, names, ordering) beyond size, which keeps it just short of fully self-sufficient.

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 no parameters and the schema is fully described, so there is nothing for the description to disambiguate. Baseline 4 applies for a zero-parameter tool.

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 (lists bootable images) and then partitions the result set into Arrakis images vs. the account's saved images, with download size. It also names the sibling entry point (rent_gpu's template_id / image) that consumes the output, so an agent can place it precisely among siblings.

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?

The mention that 'any other public image works through rent_gpu's image' routes the agent to the alternative when the desired image isn't listed, and the template_id framing implies this is the lookup step before rent_gpu. It stops short of an explicit 'call this before renting to obtain template_id' instruction or any when-not-to-use statement.

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