Lists available building blocks with names, template IDs, approximate colors, and native sizes, helping you select valid placeable elements before designing a scene.
List the building blocks scene_build_blocks can place: name, template ID, approximate colour and native size. Read this before designing a scene.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly/closed-world/non-destructive, so the safety profile is covered. The description adds value by disclosing the shape of the result — the four fields and that colour is only approximate and size is native — which matters when an agent previews layout before building.
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: the first states contents, the second states the action to take. The 'read this before' directive is appropriately placed at the end as the call-to-action, with zero 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?
With no output schema, the description correctly compensates by naming the returned fields and their approximate nature. It could go slightly further (e.g. whether the template IDs are the exact values scene_build_blocks expects, and whether the catalog is static or map-dependent), but an agent has enough 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, so there is nothing to disambiguate beyond the schema's empty object; baseline for a 0-param tool is 4. No parameter guidance is needed or missing.
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?
Specific verb (List) plus specific resource (building blocks placeable by scene_build_blocks), and it enumerates the exact fields returned: name, template ID, approximate colour, native size. It also implicitly separates itself from the other catalog siblings (image_catalog, effect_catalog, sound_catalog) by naming the consuming tool.
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?
'Read this before designing a scene' gives a clear trigger and names the downstream tool (scene_build_blocks) whose inputs come from here. There is no explicit exclusion (e.g. when to prefer image_catalog or scene_search_assets instead), so it stops short of full when/when-not guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.