ap_fill_layer

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

With no annotations, the description carries full behavioral disclosure: it pushes an undo step, fails with no_project/bad_args if no layer is selected, has a side effect on the viewport, and is the only layer operation in the plugin API. This is far more than a basic summary.

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?

The key purpose is front-loaded in the first sentence, and every subsequent sentence contributes a distinct decision-relevant fact: visible effect, workflow order, error condition, and API uniqueness. The length is justified by the lack of annotations and schema details.

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 zero-parameter tool with no annotations and no output schema, the description covers behavior, prerequisites, failures, workflow placement, and alternatives. There is no meaningful information gap left for an agent to call it correctly.

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 zero parameters and the schema is empty, so no parameter documentation is missing. The description adds meaning by identifying the implicit contextual inputs (selected layer and active material) and the failure mode when the layer state is absent.

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 first sentence names a specific verb and resource: fill the selected layer with the active material and push an undo step. It further distinguishes itself from ap_material_update by stating that only filling/painting makes node-graph edits visible, and identifies itself as the only layer-bound API operation.

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 gives an explicit working loop: ap_node_* edits -> ap_material_update -> ap_fill_layer -> ap_capture_viewport. It also warns that ap_material_update alone only recompiles the material and that nothing appears until fill/paint, so an agent knows exactly when this tool is required.

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