draw_symmetric_pixels

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

Annotations declare readOnlyHint=false and openWorldHint=false, so the agent knows this is a local mutation. The description usefully adds the mirroring behavior and axis defaults, but says nothing about whether it overwrites or blends existing pixels, which layer/frame it targets, or any return value.

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 short sentences with the core purpose front-loaded and no filler. The mode enumeration is compact, though the parenthetical phrasing ("across vertical axis_x") is slightly terse and could be misread.

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 mutation tool with 8 parameters, 25% schema coverage, and no output schema, the description covers the symmetry concept and axis defaults but omits the pixels payload shape, color format, and frame/layer targeting. An agent can grasp intent but lacks enough detail to call it correctly without inspecting the schema.

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 only 25%, so the description must carry weight; it does explain the mode enum values and that axis_x/axis_y default to the canvas centre. However, the required parameters (filename, pixels, color) and the format of the pixels array (objects with additionalProperties) remain undocumented in both schema and description.

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?

"Plot pixels together with their mirror image(s)" gives a specific verb (plot/draw), resource (pixels), and the distinguishing feature (mirror symmetry) that separates it from the sibling draw_pixels. It does not explicitly name an alternative, but the symmetry concept makes the tool's niche clear without opening the schema.

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 description explains the mode values (horizontal/vertical/both) but never states when to choose this tool over draw_pixels or mirror_layer. Usage is only implied by the mode semantics, with no when-to-use or when-not guidance.

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