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Plasticity MCP

Plasticity MCP

by Mesteriis
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
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plasticity_changes_since

Read-only

Compare the current CAD scene against a saved snapshot and return a paginated structured diff of changed B-Rep bodies, sketches, planes, materials, visibility, and groups.

Instructions

Return a structured diff from a captured scene baseline. Exact changed-body B-Rep descriptors are summarized and paginated (bodyOffset default 0, bodyLimit default 20, maximum 100); follow bodyPagination.nextOffset with expectedRevision set to current.revision. Use plasticity_body_info for detailed topology of selected bodies. The diff also reports sketch Regions, construction planes, materials, visibility, instances, groups, and selection. Check sceneChanged for a reportable scene edit; revisionChanged can be true without a reportable scene diff.

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": {
      "snapshotId": "<snapshotId>"
    },
    "name": "plasticity_changes_since"
  }
}

Input Schema

NameRequiredDescriptionDefault
bodyLimitNo
bodyOffsetNo
snapshotIdYes
expectedRevisionNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.2.0

TDQS

A4.5/5.0
Behavior5/5

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered; the description goes further by disclosing pagination mechanics (bodyOffset default 0, bodyLimit default 20, max 100), the optimistic-revision contract, and the subtle sceneChanged vs revisionChanged distinction. That is real behavioral context an agent could not infer from the schema.

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 but front-loaded: the core purpose leads, then pagination instructions, then the companion tool, then the reporting caveat. Every sentence carries information, though the enumeration of diffed categories is long.

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

Completeness4/5

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

With no output schema, the description does the work of describing the return payload (changed-body B-Rep descriptors plus regions, planes, materials, visibility, instances, groups, selection), which is substantial. Remaining gap is minor: no error/expiry behavior and only implicit explanation of how the baseline snapshot is identified.

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

Parameters4/5

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

Schema description coverage is 0%, so the description must carry parameter meaning, and it does for three of four: bodyOffset/bodyLimit defaults and maximum, and expectedRevision tied to current.revision. snapshotId is only implicitly described as the 'captured scene baseline', leaving its exact format/relationship to capture_snapshot unstated.

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 ('Return a structured diff from a captured scene baseline') and enumerates the diffed categories, so an agent can distinguish it from sibling inspection tools. It also explicitly routes topology-level detail to plasticity_body_info rather than leaving the boundary implicit.

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

Usage Guidelines4/5

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

Gives concrete operating guidance: follow bodyPagination.nextOffset with expectedRevision set to current.revision, and use plasticity_body_info for detailed topology of selected bodies. It also tells the agent to check sceneChanged for a reportable edit. It stops short of stating explicit when-not conditions or the snapshot prerequisites.

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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