MCP 3D Printer Server

merge_vertices

Combine duplicate or near-coincident vertices in an STL file within a specified tolerance to repair mesh geometry before slicing or 3D printing.

Instructions

Merge vertices in an STL file that are closer than the specified tolerance.

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": {
      "stl_path": "<stl_path>"
    },
    "name": "merge_vertices"
  }
}

Input Schema

Name	Required	Description	Default
`stl_path`	Yes	Path to the STL file to modify.
`tolerance`	No	Maximum distance between vertices to merge (in mm, default: 0.01).

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.2.9Sep 29, 2026

TDQS

B3.1/5.0

Behavior2/5

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

No annotations are provided, so the description carries the full behavioral burden. It implies mutation but never states that the file is modified in place, whether the original is preserved, what happens on failure, or how vertices are matched; only the tolerance semantics are conveyed.

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

Conciseness5/5

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

A single, front-loaded sentence with no filler; the operation, target, and merge criterion are all stated up front.

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

Completeness3/5

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

For a simple two-parameter tool with a fully documented schema and no output schema, the description is close to sufficient. However, as an unannotated mutation tool it should disclose that it rewrites the STL in place and any file-state assumptions, which it does not.

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

Parameters3/5

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

Schema description coverage is 100%, so both parameters (stl_path, tolerance) are already documented with units and default. The description's mention of 'closer than the specified tolerance' reinforces the filtering semantics but adds nothing beyond the schema's baseline.

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 (merge) and resource (vertices in an STL file) with the qualifying condition (closer than the specified tolerance), which is enough to distinguish it from siblings like scale_stl or rotate_stl. It stops short of explicitly contrasting with any sibling, so a 4 rather than 5.

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

Usage Guidelines2/5

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

There is no guidance on when to reach for this tool versus alternatives such as modify_stl_section or the blender_mcp_* editing tools, nor any mention of prerequisites like an existing valid STL file. The purpose is implied but selection context is absent.

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