add_sketch

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

Annotations already declare destructiveHint=true, readOnlyHint=false, and non-idempotent, so the mutation profile is covered structurally. The description adds two genuinely useful behavioral facts: the unit convention (mm, degrees, kg) for all public geometry values, and that the result exposes verified measurements plus error evidence. It still omits what gets modified or destroyed (does it replace an existing sketch?), whether a document must be active, and how failures are reported.

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?

Three short sentences, so nothing is bloated, but the opening clause about the "independent native SOLIDWORKS engine" is filler that consumes the most prominent position. The closing sentence about inspecting measurements is vague rather than actionable, so the space is not well spent.

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?

This is a destructive, geometrically complex tool with three required parameters, a nested segment union type, 0% schema documentation, and no output schema. The description covers units only and leaves an agent unable to construct a valid segments payload or plane reference without trial and error.

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 description coverage is 0% across four parameters, including a deeply nested segments array with oneOf line/arc/spline branches plus center, tangent, and through fields that carry no documentation at all. The description only supplies the mm unit convention, which partially explains start_mm and coordinate arrays but leaves plane format, segment geometry encoding, and the optional name completely unexplained.

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?

"Add sketch" gives a verb and a resource, but the description never says what a sketch is composed of here (a plane, a start point in mm, and a list of line/arc/spline segments), nor how it differs from siblings like read_sketch, extrude_sketch, cut_sketch, or add_extruded_spline. The phrase "independent native SOLIDWORKS engine" describes the backend rather than the action, so an agent gets only a vague sense of the operation.

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?

There is no guidance on when to use this versus extrude_sketch, cut_sketch, add_extruded_profile, or add_extruded_spline, and no prerequisites such as needing an open document, an active part, or a valid plane reference. The agent must infer everything from the name and schema.

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