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

With annotations already declaring destructiveHint=true and openWorldHint=true, the description adds genuinely useful context: where downloaded files land (workspace inputs/) and what the call returns (dimensions and path). The one real gap is that it never says what the destructive aspect replaces — presumably the existing camera reference image — so the agent cannot tell the user what will be overwritten.

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 short sentences, each carrying distinct information: the action, the accepted inputs, the side effect, and the return value. The core action is front-loaded and there is no filler.

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 two-parameter mutation with no output schema, the description covers action, input modes, download destination, and return shape — enough to call it correctly. It falls short only on the prerequisites for the mutation and on what the destructive flag actually destroys.

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 100%, so the image parameter's three accepted forms are already documented in the schema and the description largely restates them. It adds nothing about operation_name beyond what the schema says, and no format details (e.g. size limits, whether relative paths are rooted at the project). Baseline 3 applies where the schema does the heavy lifting.

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 opens with a specific verb and resource: "Put a reference PNG/JPEG behind the scene camera," which is concrete and unambiguous. It does not, however, differentiate itself from related siblings such as compare_reference_render or render_project_image, so an agent must infer the boundary from the name alone.

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?

Usage is only implied by the stated purpose; there is no explicit when-to-use or when-not-to-use guidance, and no mention of prerequisites such as an open Blender session or an active project. The accepted input forms are listed, but that is about invocation rather than choosing this tool over an alternative.

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