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U-C4N
by U-C4N

Drawing Settings (read / change)

drawing_settings

Read or change AutoCAD drawing settings by friendly name, like units and limits, to avoid memorizing system variables. Omit arguments to get a full snapshot.

Instructions

Read or change common AutoCAD drawing settings by friendly name.

A convenience facade over the system variables (INSUNITS, LUPREC, LTSCALE, DIMSCALE, DIMTXT, DIMASZ, DIMDEC, DIMDSEP, DIMZIN, TEXTSIZE, OSMODE, LIMMIN/ LIMMAX, GRIDMODE/GRIDUNIT, SNAPMODE/SNAPUNIT, ORTHOMODE, AUTOSNAP/POLARANG, PSLTSCALE, CANNOSCALE, LUNITS, AUNITS, DIMSTYLE, TEXTSTYLE) so the user can say "set units to mm, limits to A3 and the grid on" without memorising sysvar names. Call with no argument for a full snapshot; a write returns applied, changed ({key: [old, new]} — only what moved) and errors.

dim_text_height / dim_arrow_size / dim_decimals / decimal_separator / zero_suppression shape the dimension — text_size is TEXTSIZE, the height of a standalone TEXT entity, and does not touch dimensions.

Refusals, per key, nothing else rolled back: an unknown key; a value outside its range (grid/snap spacing > 0, polar_angle 0–360, precision 0–8, …); a malformed limits or annotation_scale; osmode / polar / polar_angle on the headless engine (capability: registry_sysvar — AutoCAD keeps them in the registry, a file cannot, and a headless snapshot reports them as None); dimstyle / textstyle when the backend has no styles contract. On the live engine annotation_scale must name a scale in the drawing's scale list (SCALELISTEDIT) and AutoCAD refuses the write on a paper-space layout with no active viewport; the headless engine adds the scale, seeding AutoCAD's default list first when the drawing has none, and refuses it on an R12 file (no OBJECTS section, so the value would vanish at save — save as R2000 or newer first; limits/grid/ortho survive). Headlessly, grid/snap are stored on the active VPORT and the annotation scale in the variable dictionary — the places AutoCAD reads them from.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
settingsNoOmit to READ every setting; pass a dict to CHANGE them. Friendly keys: units (mm/cm/m/inch/feet), linear_precision, angular_precision, ltscale, dimscale, dim_text_height, dim_arrow_size, dim_decimals, decimal_separator ("." or ","), zero_suppression, text_size, point_mode, point_size, osmode, fillet_radius, limits ([[xmin,ymin],[xmax,ymax]]), grid (bool), grid_spacing, snap (bool), snap_spacing, ortho (bool), polar (bool), polar_angle (degrees), psltscale (bool), annotation_scale ("1:50"), linear_units (decimal|engineering|architectural|fractional|scientific), angular_units (degrees|dms|grads|radians|surveyor), dimstyle, textstyle (current style names). Example: {"units": "mm", "limits": [[0, 0], [420, 297]], "grid": true}.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv1.6.0
    • changedInput schema / properties / settings / description
      Previous value: -"Omit to READ every setting; pass a dict to CHANGE them. Friendly keys: units (mm/cm/m/inch/feet), linear_precision, angular_precision, ltscale, dimscale, dim_text_height, dim_arrow_size, dim_decimals, decimal_separator (\".\" or \",\"), zero_suppression, text_size, point_mode, point_size, osmode, fillet_radius. Example: {\"units\": \"mm\", \"dimscale\": 1.0, \"dim_text_height\": 3.5}."New value: +"Omit to READ every setting; pass a dict to CHANGE them. Friendly keys: units (mm/cm/m/inch/feet), linear_precision, angular_precision, ltscale, dimscale, dim_text_height, dim_arrow_size, dim_decimals, decimal_separator (\".\" or \",\"), zero_suppression, text_size, point_mode, point_size, osmode, fillet_radius, limits ([[xmin,ymin],[xmax,ymax]]), grid (bool), grid_spacing, snap (bool), snap_spacing, ortho (bool), polar (bool), polar_angle (degrees), psltscale (bool), annotation_scale (\"1:50\"), linear_units (decimal|engineering|architectural|fractional|scientific), angular_units (degrees|dms|grads|radians|surveyor), dimstyle, textstyle (current style names). Example: {\"units\": \"mm\", \"limits\": [[0, 0], [420, 297]], \"grid\": true}."
  2. Changed1 schema field changedv1.5.1
    • changedInput schema / properties / settings / description
      Previous value: -"Omit to READ every setting; pass a dict to CHANGE them. Friendly keys: units (mm/cm/m/inch/feet), linear_precision, angular_precision, ltscale, dimscale, text_size, point_mode, point_size, osmode, fillet_radius. Example: {\"units\": \"mm\", \"dimscale\": 1.0, \"linear_precision\": 2}."New value: +"Omit to READ every setting; pass a dict to CHANGE them. Friendly keys: units (mm/cm/m/inch/feet), linear_precision, angular_precision, ltscale, dimscale, dim_text_height, dim_arrow_size, dim_decimals, decimal_separator (\".\" or \",\"), zero_suppression, text_size, point_mode, point_size, osmode, fillet_radius. Example: {\"units\": \"mm\", \"dimscale\": 1.0, \"dim_text_height\": 3.5}."
  3. First observedv1.4.0

TDQS

A4.6/5.0
Behavior5/5

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

Annotations only declare readOnlyHint=false and destructiveHint=false; the description goes far beyond by disclosing that refusals are per-key with nothing else rolled back, which keys fail on the headless engine (osmode/polar, dimstyle/textstyle), the live-engine scale-list and paper-space viewport constraints, and the R12 no-OBJECTS save hazard. This is unusually rich behavioral disclosure.

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?

Front-loaded with the core read/change purpose, then progressively more specialized engine caveats. Every sentence carries operational information, though the long parenthetical sysvar list and multi-clause refusal paragraphs make it denser than strictly necessary.

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?

An output schema exists, so return-shape detail is optional, yet the description still names the write payload (applied, changed, errors). Combined with the refusal and engine-capability coverage, an agent has everything needed to call this correctly across live and headless backends.

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 coverage is 100% and the schema already enumerates friendly keys and value formats, so baseline is 3. The description adds genuine semantics beyond the schema: it distinguishes dimension-shaping keys (dim_text_height, dim_arrow_size, etc.) from text_size (TEXTSIZE, standalone TEXT entity), and states refusal ranges such as grid/snap spacing > 0 and precision 0–8.

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 pair (read/change) and resource (common AutoCAD drawing settings by friendly name), and explicitly frames itself as a facade over named system variables. This distinguishes it from the raw system_get_variable / system_set_variable siblings without the agent needing to open 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 Guidelines4/5

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

Gives explicit invocation guidance: 'Call with no argument for a full snapshot', pass a dict to write, plus a per-key refusal catalogue. It implies rather than names the raw sysvar alternatives (system_set_variable), so it stops short of a full when-not-to-use statement, but context for use is clear.

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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