sketch_circle

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

Annotations already declare this is a non-read-only, non-destructive, non-idempotent mutation, so the safety profile is covered. The description adds the 'open sketch' context requirement, which is genuinely useful. However, it does not warn that repeating the call creates a duplicate circle (the annotation says idempotentHint=false) nor what happens to the active sketch.

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?

One sentence, zero filler, with the distinguishing detail (diameter, not radius) and the unit front-loaded. Nothing could be removed without losing meaning.

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?

An output schema exists, so return values need not be described, and annotations cover the mutation profile. But for a 3-parameter sketch tool with 33% schema coverage, the description leaves the centre-coordinate defaults and the sketch-precondition consequences unstated, which is a meaningful gap for correct invocation.

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 only 33% – only diameter_mm is documented in the schema, while center_x_mm and center_y_mm have bare titles and default values of 0. The description compensates partially by tying 'centre' to a coordinate pair and stressing DIAMETER rather than radius, but it never states that the centre defaults to the origin, leaving real ambiguity.

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?

Specific verb+resource ('Draws a circle') with a stated scope ('in the open sketch') and the key unit/semantics ('DIAMETER (mm)'). It lets an agent distinguish it from sketch_arc or sketch_ellipse by shape, though it does not explicitly name those siblings.

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?

The phrase 'in the open sketch' implies the precondition that a sketch must already be active (i.e. start_sketch must have run), but this is left implicit. There is no explicit statement of when to prefer this over sketch_arc/sketch_ellipse or what to do if no sketch is open.

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