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lucasr1b

sketchdex

by lucasr1b
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JavaScript
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add_elements

Append new Excalidraw elements to an existing scene without altering what's already there, ideal for adding diagrams, text, boxes, arrows, or detail strokes.

Instructions

Append elements to a scene, leaving everything already there untouched. The usual way to draw something new.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
labelYesShort description of what this change is doing, e.g. 'add the dog illustration'. Shown next to the snapshot in the history sidebar, which is how the user decides whether to keep or revert it. Always set it.
sceneYesScene id, exact name, or a unique part of the name. Use list_scenes if unsure.
elementsYesExcalidraw elements. Any field of a real element is honoured verbatim; what you omit gets a valid default (id, index, seed, version are generated). USE THIS FOR diagrams, layout, text, boxes, arrows, and detail strokes on top of something already drawn. For anything that has to LOOK LIKE something - a character, creature, object, vehicle, logo, illustration - do NOT assemble it from shapes here. Write it as one SVG and call import_svg. Shapes stacked by hand come out as a pile of parts (fat, seamed, toy-like) every time; one SVG comes out as one drawing. Types: rectangle ellipse diamond arrow line text freedraw frame. Fields: x y width height angle, strokeColor, backgroundColor (the fill), fillStyle solid|hachure|cross-hatch, strokeWidth 1|2|4, strokeStyle, roughness 0|1|2, opacity, roundness, fontSize, fontFamily (5 hand-drawn), textAlign, groupIds, points [[0,0],[dx,dy],...] relative. y points down. TEXT WRAPS: give a text element a `width` and prose is wrapped to it with the real font metrics (height follows); no width = one line per \n, sized exactly. Never break long paragraphs by hand. THE LOOK IS HAND-DRAWN. This is Excalidraw. roughness 1 (default) on everything; native rectangle/ellipse/arrow rather than 4-point lines; sparse points with roundness {type:2} for a curve (dense points look furry, not sketchy); hand-drawn font. Detail is a few extra strokes, never more parts. COLOUR IS FLAT. Solid fills, one colour per part, and the wobbly outline does the rest - that is the Excalidraw look. Do not shade: no hachure or cross-hatch as texture, no gradients faked with stacked shapes, no drop shadows. If a part must read as darker, give it a darker solid hex. Reserve hachure/cross-hatch for something that IS hatched (a cutaway, a glass pane). PAPER AND INK. Nothing is inverted for display: every hex shows exactly as written. New scenes are dark paper (#121212). Anything drawn without a strokeColor gets ink that contrasts with the paper (#e9ecef on dark, #1e1e1e on light); describe_scene reports `background` and `ink`. Any hex is fine - character colours are character colours on any paper. SHORTHAND. label on a shape adds centred bound text; ref names an element and start/end on an arrow bind to it. Generated geometry is an element whose type is polygon|star|arc|capsule|path, e.g. {"type":"path","points":[[0,0],[40,30],[90,10]],"closed":true} smooth curve through the points polygon {sides,cx,cy,r} star {points,cx,cy,r,innerRatio} arc {cx,cy,r,from,to} capsule {x,y,width,height,radius} repeat {count,dx,dy | cols,rows | around:{cx,cy}} and mirror {axis:'vertical',at} multiply one spec evenly. These are for furniture - rings, plates, arrays - not for bodies.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.2

TDQS

A3.8/5.0
Behavior3/5

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

With no annotations, the description carries the full behavioral burden, and it does disclose the key trait: this operation is additive and leaves existing content untouched. It says nothing about permissions, history/snapshot implications, or failure modes for an invalid scene id, so disclosure is partial but meaningful.

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?

Two short sentences with zero waste, front-loading the action and then the distinguishing non-destructive property. Nothing repeats the name or pads the text.

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?

For a complex drawing tool the description is deliberately thin, but the exceptionally rich elements schema covers types, defaults, styling conventions, and import_svg routing, and no output schema exists to explain. The only real gap is the absence of any note on what the call returns or how the change appears in history.

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 the schema already documents label, scene, and the elements array in depth. The top-level description adds no parameter syntax or format detail beyond that, which is exactly the baseline-3 case where structured fields do the heavy lifting.

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?

Specific verb plus resource ('Append elements to a scene') with an explicit non-destructive qualifier ('leaving everything already there untouched'). That qualifier cleanly separates it from siblings like update_elements, replace_scene, and delete_elements, so an agent can pick it without opening another schema.

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?

'The usual way to draw something new' implies this is the default entry point for adding content, which is useful framing. However, the description itself gives no explicit when-not conditions or named alternatives; the important routing guidance (use import_svg for anything that must look like a character/object) lives in the schema text, not here.

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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