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Houdini MCP

Houdini MCP

by beatreichenbach
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
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execute_python

Run Python code directly inside Houdini when standard MCP actions cannot complete a task, using a justification to document why this last-resort execution is needed.

Instructions

Execute arbitrary Python code inside Houdini. LAST RESORT only.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "code": "<code>",
      "justification": "<justification>"
    },
    "name": "execute_python"
  }
}

Input Schema

NameRequiredDescriptionDefault
codeYes
justificationYes
return_expressionNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

C2.8/5.0
Behavior2/5

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

With no annotations, the description carries the full burden, and it only hints at risk via 'arbitrary' and 'LAST RESORT.' It says nothing about sandboxing, whether scene mutations are possible, error behavior, timeouts, or what the tool returns for the supplied code.

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?

Two short sentences with the core capability front-loaded and no wasted words. The brevity is efficient, though it edges into under-specification given the tool's complexity.

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

Completeness2/5

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

This is an arbitrary-code-execution tool with no annotations, no output schema, and zero parameter documentation, yet the description is two sentences. For a tool this powerful and this under-specified structurally, far more context is needed about execution scope, return handling, and the required justification argument.

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

Parameters1/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 0% and the description mentions no parameters at all. The required 'justification' parameter and the non-obvious 'return_expression' parameter are fully undocumented, so an agent cannot know how to populate them or why justification is mandatory.

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

Purpose4/5

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

States a specific verb and resource ('Execute arbitrary Python code inside Houdini'), which is enough to distinguish it from an HScript executor by language alone. It never names a sibling explicitly, so it stops just short of full differentiation.

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

Usage Guidelines3/5

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

'LAST RESORT only' is a genuine usage constraint that tells the agent to prefer other tools first, which is more than most definitions offer. However, it never names which alternatives to try first or what conditions make this the right choice, leaving the agent to infer the actual decision rule.

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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