blender_grease_pencil_markup

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

With no annotations provided, the description carries the behavioral disclosure burden. It does add one meaningful behavioral detail: it uses Pillow when available and otherwise falls back to the Blender compositor. It does not disclose output behavior details, such as whether the output file replaces existing files, what happens on unsupported annotation coordinates, or whether the original render is modified.

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 description is compact and front-loaded: the core action appears in the first sentence, and the fallback implementation note is a useful second sentence. There is no filler or redundant restating of 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 moderately complex tool with nested annotation objects, the combination of the concise description and the thorough schema gives an agent enough to invoke it correctly. The fallback behavior is disclosed, and the schema covers coordinates, types, and defaults. The main gap is that the description does not mention what the tool returns or whether the output path is confirmed, but the absence of an output schema makes this a minor omission.

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%, so the schema already documents every parameter meaningfully. The description contributes some semantic context by naming the annotation types (arrows, circles, rectangles, text), which maps to the type enum, but it does not add material information beyond the schema.

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 states a specific verb ('Overlay'), a clear resource ('a rendered image'), and enumerates the annotation types offered. It mostly distinguishes itself from the scene-oriented blender_annotation_* and blender_grease_pencil_create siblings by emphasizing 'on a rendered image', though it does not explicitly name those alternatives.

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 intended use is implied: apply 2D markup to a rendered image rather than adding Grease Pencil annotations to the 3D scene. However, there is no explicit guidance about when to choose this tool over blender_annotation_add/blender_annotation_text, nor any stated exclusions or prerequisites such as requiring a prior render.

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