set_viewport_renderer

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

No annotations are provided, so the description carries the full burden. It adds useful behavioral detail beyond the action itself: the result 'reports the delegate that is actually active afterwards, read back from Houdini rather than inferred from a setter not raising.' This tells the agent how to interpret the outcome and that the tool verifies rather than assumes.

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 purpose is front-loaded and the prose is generally tight, but the Args block repeats the renderer parameter twice with slightly different wording. This duplication is a structural defect and makes the description less clean than it should be.

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 two-parameter viewport setter with no output schema, the description is largely sufficient: it explains why to use it, what the result reflects, and what renderer values are acceptable. It does not exhaustively cover edge cases like pane_name resolution behavior, but it is complete enough for an agent to call the tool correctly in the stated lookdev workflow.

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. It does add valuable renderer semantics with examples and 'case-insensitive partial match,' but the pane_name parameter is only described as 'Pane tab name,' adding little beyond the schema. The duplicate 'renderer' line also creates ambiguity and wastes an opportunity to fully document the parameters.

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 opens with a specific verb and resource: 'Set the viewport's Hydra rendering delegate for live preview.' It clearly distinguishes this from sibling rendering tools by contrasting live preview with 'writing full renders to disk,' so an agent can tell it apart from render_viewport and related viewport setters.

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 it: 'during lookdev to preview materials and lighting directly in the viewport.' It also gives an implicit exclusion by saying 'instead of writing full renders to disk,' although it does not name an alternative tool explicitly.

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