Set an HScript or Python expression on a Houdini parameter to drive its value programmatically.
Set an expression on a parameter.
Args: node_path: Node path. parm_name: Parameter name. expression: Expression string. language: "hscript" (default) or "python".
| Name | Required | Description | Default |
|---|---|---|---|
| language | No | hscript | |
| node_path | Yes | ||
| parm_name | Yes | ||
| expression | Yes |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations are absent, so the description must carry behavioral disclosure. It only says 'Set an expression on a parameter' – implying a mutation but no details on side effects, error conditions, or return behavior. There's no mention of whether it overwrites existing expressions, whether it triggers a cook, or what happens if the parameter is missing.
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?
Extremely concise: one sentence + an Args list. Information is front-loaded and there is no fluff. The format is easy to scan.
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 tool with no annotations and 0% schema coverage, this description is too sparse. It lacks examples or format guidance for node_path, parm_name, or expression syntax. An agent attempting to construct a valid call would have to infer the expected expression format from elsewhere. Sibling tools like set_parameter and evaluate_expression have richer context, making this feel incomplete.
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%, so the description is the only source. It lists all four parameters with terse definitions: node_path, parm_name, expression, language. It does clarify that language can be 'hscript' or 'python' but omits syntax examples or path formats, leaving significant ambiguity for an agent.
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 'Set an expression on a parameter' – a specific verb, resource, and object. It clearly distinguishes from set_parameter (which sets values) and get_expression/evaluate_expression. However, it could be more explicit about the difference between setting an expression vs a value, but the intended purpose is clear.
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?
No guidance on when to use this tool instead of alternatives. It doesn't mention when to prefer this over set_parameter or evaluate_expression. The description is purely functional, leaving the agent to infer usage from names.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.