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

With no annotations at all, the description carries the full burden, and it does disclose two useful facts: the concrete cost (3 credits) and the return shape ({ processedImage }). It still omits whether the original artwork is preserved or replaced, what happens to image dimensions/aspect ratio, and any size or resolution limits — material gaps for an unannotated mutation tool.

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?

Two compact sentences, front-loaded with the core action, then return value and cost. Nothing is wasted and nothing is buried.

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 3-parameter, fully documented-schema tool the description covers the essentials of action, output, and price. It falls short on what an agent most needs before invoking: whether the operation is destructive to the source artwork and whether credits are consumed on failure.

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%, with the enum, required flag, and default for direction all documented in the schema, so the baseline applies. The description adds no meaning beyond it — notably it never mentions the context prompt or the directional options, which are the two parameters that most affect output.

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?

"Expand (outpaint) an image beyond its borders" pairs a specific verb with a specific resource and even supplies the industry synonym (outpaint), so the intent is unambiguous. It does not, however, distinguish itself from the many other image-transform siblings (enhance_image, aspect_ratio_change, create_image), leaving the agent to infer the boundary.

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?

There is no when-to-use or when-not-to-use guidance, no mention of prerequisites (e.g., minimum image size or credit balance), and no routing to any alternative for resize/crop-style needs. The agent must guess the selection criteria from the name alone.

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