merge_coplanar

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

With no annotations, the description carries the disclosure burden and does well: it declares the mutation is a single undo step, that it shares the post-check and change report of move_plane, that dry_run previews, and that ignore_back_material discards a material. It still omits any permission/context requirements or failure modes (e.g. what happens with locked groups).

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 sentences, front-loaded with the operation and its conditions, then behavioral facts, then the preview route. No filler and nothing buried.

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 mutation tool with no annotations and no output schema, the description covers the essentials: what changes, reversibility, preview mechanism, and material edge cases. The deferred 'same change report as move_plane' leaves the return shape implicit, which is a minor gap rather than a blocker.

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 67%: `group` and `ignore_back_material` are documented in the schema, while `dry_run` is not — but the description supplies that meaning explicitly ('or dry_run:true here'). The description therefore closes the one real gap rather than merely restating the schema.

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 and resource ('erase the seam edges between coplanar faces ... merging them back into single faces') with the precise preconditions (same orientation, same front/back materials, same group). This is enough to separate it from adjacent siblings like weld_vertices or audit_geometry without opening a schema.

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 an explicit preview path: inspect audit_geometry's mergeable_coplanar_seams first, or run with dry_run:true here. That is clear routing guidance for a mutation tool, though it never states when the operation should be avoided (e.g. non-coplanar or intentionally seamed geometry).

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