render_preview

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

With no annotations provided, the description carries the full behavioral burden and does well: it declares the output quality ('deliberately low, up to 1280x720, few samples, denoised'), cost model ('same GPU cost as one 720p frame'), return values including warnings and expiry ('24h after last use'), and reuse semantics ('reuse it without re-uploading'). The main gap is that it doesn't explicitly state potential side effects like whether a job consumes billing immediately or whether partial failures are returned as errors, but overall it is substantially informative.

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 front-loaded with the core purpose and then provides usage and parameter details in a logical flow. It is somewhat long but most sentences earn their place by clarifying behavior; a few phrases like the full iteration advice could be trimmed without losing essential information.

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?

Given no output schema, no annotations, and 9 parameters at 0% schema coverage, the description does a decent job covering return values and the frames parameter but omits explanation for five important parameters (camera, width, height, samples, out_dir). For a tool with this complexity, a more complete parameter guide is needed.

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 0%, so the description must compensate, and it partially does: it explains scene_path (a .blend file OR a bpy Python script), scene_script (bpy code as text), scene_id (from a previous call), and frames (with exact syntax and tiling behavior). However, width, height, samples, camera, and out_dir receive no explanation, leaving meaningful gaps for a 9-parameter tool.

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 and resource ('Render a fast, cheap preview of a Blender scene on a JANCTION GPU') and clearly distinguishes itself from siblings by emphasizing it is a preview, with an explicit handoff to render_final. An agent can identify exactly what the tool does without reading other definitions.

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 explicitly states when to use this tool ('when the user is making 3DCG with Blender and wants to see how it looks, but has no GPU or local rendering is slow'), provides the alternative action ('call render_final' once satisfied), and describes the iterative workflow between them. This is a strong example of routing guidance.

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