add_disc

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

With no annotations, the description carries the full burden and does well: it discloses the build orientation (+Z with flat faces at +/-Z), the return value ('Returns mass properties'), and the prerequisite. It does not describe failure modes or what happens if the part is not open, which keeps it from a 5.

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?

Front-loaded with the core definition, then composition, defaults, return value, and prerequisite in a tight sequence. The phrase 'off it, its x and y are dimensions' is compact but slightly cryptic; otherwise every sentence earns its place.

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?

For a 5-param mutation tool with no annotations, no output schema, and 0% schema coverage, the description covers geometry, orientation, composition, defaults, return value, and prerequisite. It omits the meaning of diameter/thickness and error behavior, but is largely complete.

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 0%, so the description must compensate. It adds meaning for x_mm/y_mm (centre defaults to origin; off-origin they are dimensions), but says nothing about diameter_mm, thickness_mm, or name. It partially compensates for the coverage gap rather than fully closing it.

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 (Create) and resource (disc/puck/flange) and defines the geometry precisely: 'a circle extruded along +Z, centred at (x_mm, y_mm)'. This cleanly distinguishes it from siblings like add_cylinder, add_box, and add_extruded_profile.

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?

Gives a clear prerequisite ('Use new_part first') and explains composition partners (add_hole, add_circular_pattern for bolt circles). It stops short of an explicit when-not-to-use versus add_cylinder, but the context is strong enough to route correctly.

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