set_world

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

With no annotations, the description carries the full burden and does so well: it discloses error behaviour for unknown HDRI names, renderer support (eevee and cycles), the persistence of the transparent flag across calls, and that visible_to_camera=false keeps HDRI for lighting/reflection while the camera sees the plain colour. This is exactly the kind of state and side-effect disclosure a mutation tool needs.

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?

Dense but front-loaded: it opens with the core operation and then explains precedence, HDRI specifics, and flags in order of importance. Every sentence carries information, though the multi-clause final lines about transparent and visible_to_camera could be tightened slightly.

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 7-parameter tool with no annotations, no param descriptions and no output schema, the description supplies everything an agent needs: value formats, precedence, state persistence, error behaviour and renderer compatibility. Nothing material is missing.

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 documents every parameter: color's '#rrggbb' or [r,g,b] (0-1) form, preset, strength as a multiplier, hdri as path or builtin name, rotation_deg as a Z turn, visible_to_camera, and transparent. No parameter is left ambiguous.

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?

States a specific verb and resource ('Set the background and ambient light') with the two concrete modes (plain colour vs HDRI image), which cleanly separates it from sibling lighting tools like add_light, set_material and setup_lighting. An agent can tell what this mutates 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?

Gives clear precedence rules ('An explicit color wins over the preset colour'; 'With neither colour, preset nor hdri only the strength changes') and reset semantics ('A later call without hdri and with a colour or preset makes the world a plain colour again'). It does not explicitly route the agent away from alternatives such as add_light or setup_lighting, so it stops short of a 5.

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