set_viewport_renderer

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

With no annotations, the description carries the full behavioral burden. It usefully discloses return semantics ('the delegate that is actually active afterwards, read back from Houdini rather than inferred from a setter not raising'), but says nothing about persistence, reversibility, permissions, or failure modes.

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 two prose sentences are front-loaded and efficient. However, the Args block is malformed: renderer is documented twice with overlapping text, which is wasteful and confusing, violating the 'every sentence earns its place' bar.

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 2-parameter tool with no output schema, the description covers purpose, when-to-use, accepted values, and return semantics. The main gap is the under-specified pane_name parameter and any note on failure or persistence behavior.

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 coverage is 0% and the schema has no enum, so the description's accepted values ('GL', 'Storm', 'Karma CPU', 'Karma XPU') and matching rule ('case-insensitive partial match') are genuinely additive. pane_name is only glossed as 'Pane tab name', leaving its optionality and default behavior undocumented.

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 opening sentence gives a specific verb and resource ('Set the viewport's Hydra rendering delegate for live preview'), which an agent can distinguish from sibling viewport tools like set_viewport_camera, set_viewport_display, and render_viewport. It does not explicitly name siblings to route against, so it falls short of a 5.

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 provides clear usage context ('Use this during lookdev to preview materials and lighting directly in the viewport instead of writing full renders to disk'), implicitly routing the agent away from render-producing tools. No explicit exclusion list or named alternative tool, so no 5.

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