weld_vertices

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 that it is one undo step, that it aborts if a weld would split or fold a face, that cross_group leaves vertices as separate points, and that results surface in the near_coincident_vertices report delta. Auth/permission requirements are not covered, and dry_run/allow_splits effects are never described.

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-loads the core purpose in the first clause, then layers scope distinctions. Dense but every sentence adds behavioral value; slightly run-on across the cross_group explanation.

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?

Given a 6-param mutation tool with no output schema, the description covers intent, scoping, abort behavior, undo semantics, and units well enough to call it correctly. The unmentioned dry_run and allow_splits flags are the main remaining gap.

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% (4 of 6 params documented), and the description meaningfully extends the keep parameter ('moves the nested one', default 'outer') and the cross_group behavior. However, dry_run and allow_splits are undocumented in both the schema and the description, leaving two mutation-affecting flags 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?

States a specific verb and resource ('Merge near-coincident vertex pairs in a group by moving one onto the other') and immediately qualifies the default scope (same entities collection) versus the cross_group variant. An agent can distinguish it from siblings like merge_coplanar or move_entity without opening the 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 clear context for use, including the practical symptom it fixes ('the deleting a line deletes the wall problem') and the exact condition that selects cross_group (vertices in different groups/components). It does not explicitly name or rule out sibling alternatives, but the when-to-use framing is strong.

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