Create arcs

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

Annotations already declare readOnlyHint=false and idempotentHint=false, so a mutation is expected. The description nonetheless adds real value: the CCW storage quirk (clockwise arcs come back with begin/end swapped), the active-window database targeting with storyIndex default, and the per-item failure semantics ('one failing item does not stop the others') with the [{guid,type}|{error}] return shape. This is richer than the annotations alone, but it is one of many traits and does not describe auth or limits, so a 3 reflects solid-but-not-exhaustive disclosure.

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

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

Dense but front-loaded with the purpose, then forms, then placement, then return/error behavior, then follow-up tools. Every sentence carries information; the only cost is high density that a hurried reader must parse carefully.

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

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

With no output schema, the description compensates by specifying the return shape and partial-failure behavior. Combined with placement rules, defaults, the elliptical-arc options, and the modify/get follow-ups, nothing an agent needs to invoke this correctly is missing.

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

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

Schema coverage is 100%, so the baseline is 3, but the description adds compositional meaning the schema cannot: it explains how the parameters combine into three distinct arc forms, the degrees/CCW convention, and the sign convention for arcAngle (+ = CCW). That goes beyond the per-field definitions.

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

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

States a specific verb+resource ('Draws 2D circular or elliptical arcs') and immediately distinguishes itself by naming the sibling for full circles (create_circles) and the related line/circle creation tools. An agent can tell at a glance this is the arc-creation tool, not a line or circle tool.

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

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

Explicitly lays out three alternative ways to define an arc (A: center+radius+angles, B: begin+end+arcAngle, C: begin+through+end) and routes to create_circles for full circles, modify_elements for later edits, and get_element_details for reads. It also states the placement constraint (active window; a 3D window cannot hold 2D elements), which is a genuine when-this-works condition.

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