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

Annotations already declare destructiveHint=true, readOnlyHint=false, and openWorldHint=false, so the safety profile is covered. The description adds a genuine constraint — the URL must persist ('will still be there tomorrow') — but says nothing about what happens to existing images, auth needs, or reversibility.

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 tight sentences with the action front-loaded and no filler. The colloquial 'will still be there tomorrow' is slightly informal but conveys a concrete requirement efficiently.

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 destructive, nested-object mutation with no output schema, the description covers input sourcing well but omits what a mutation replaces, whether slots can be cleared, and the effect of an invalid url. Adequate but with visible gaps.

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 50% (only the images object is documented), so the description must compensate, and it does: it explains that the map keys are slot tokens sourced from uichemy_template_slots and values are urls from uichemy_upload_image or any https url. projectId remains unexplained, holding it below 5.

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 (put pictures into image slots) that an agent can distinguish from siblings like set_logo or upload_image. It doesn't explicitly mark the boundary against set_image_display or edit_image_masked, but the action and target are unambiguous.

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 routes the agent to the correct prerequisite tools: slot tokens from uichemy_template_slots and urls from uichemy_upload_image. That is real when-and-where guidance, though it gives no exclusion cases (e.g. use set_logo instead for logos).

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