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by healkeiser
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press_button

Trigger a Houdini node's button parameter, such as Stash Input or Reload Geometry, then read its errors and warnings; cook the node to refresh stale results.

Instructions

Press a button parameter — "Stash Input", "Reload Geometry", an asset's own Build button — and read the node's errors and warnings afterwards.

The call holds until the callback returns, with no deadline. A callback that opens a dialog blocks Houdini's main thread and this bridge with it; read the button's script first if in doubt. A Python callback that RAISES does not hang anything: the bridge runs it rather than pressButton(), and its error comes back as this call's error. callback_route says how the press ran: python, hscript or native (a built-in action). For a Save to Disk or a render use write_cache / start_render, which report a verdict.

A press usually only dirties the node, so errors/warnings are from its last cook unless cook=True; without it needs_cook says whether they are stale (a cook that failed leaves it True too). has_script_callback is False for built-in buttons that still do work (File's Reload, Stash's Stash Input).

A parm that is not a button and has no callback is refused: pressing it does nothing. The small action button beside a field ("Create spare parameters" on a VEXpression) runs with action=True; an action that opens a picker holds the bridge like a dialog does.

Args: node_path: Node that owns the button. parm_name: The button parameter's name. arguments: Optional kwargs handed to the callback script; values must be int, bool, float or str. cook: Cook the node after the press so errors describe the result. action: Run the parm's action button (script_action) instead of its callback.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
cookNo
actionNo
argumentsNo
node_pathYes
parm_nameYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changedv2.24.1
    • addedInput schema / additionalProperties
      Added value: +false
    • addedInput schema / properties / action
      Added value: +{
+  "default": false,
+  "title": "Action",
+  "type": "boolean"
+}
  2. Addedv2.18.0

TDQS

A4.9/5.0
Behavior5/5

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

No annotations exist, so the description carries the full burden and does so richly: the call blocks indefinitely with no deadline, dialogs block Houdini's main thread, a raising Python callback does not hang but surfaces as this call's error, and callback_route reports python/hscript/native. It also explains errors/warnings staleness via cook and needs_cook.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Dense and mostly front-loaded, with each paragraph covering a distinct concern (blocking, callback_route, cook/staleness, refusal). It is long and prose-heavy, so a skilled agent has to parse several sentences, but no sentence is dead weight.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a complex, blocking, side-effecting tool with no annotations and no output schema, the description covers blocking behavior, error/warning staleness, callback_route, has_script_callback, refusal semantics, and the action button. An agent has everything needed to call it correctly and interpret the result.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

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 does: node_path, parm_name, arguments (with allowed value types int/bool/float/str), cook (cook so errors describe the result), and action (run script_action instead) are all explained with semantics beyond their names.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Press a button parameter') and instantly names concrete instances (Stash Input, Reload Geometry, Build button). It also distinguishes itself from siblings write_cache and start_render, so an agent can route correctly without opening any schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicit routing: use write_cache/start_render for saves and renders, read the button's script first if a callback might open a dialog, use action=True for the field's action button. It also states the refusal condition for non-button parms without callbacks. When-to-use, when-not, and alternatives are all present.

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

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