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

Annotations already declare readOnly=false, idempotent=false, destructive=false, so safety is covered. The description adds a genuinely useful behavioral detail: the global unit convention (cm not mm, angles in degrees) applies unless a parameter overrides. It says nothing about what happens to a pre-existing thread, failure modes, or whether the operation is reversible.

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?

Two sentences, front-loaded with the action and resource, followed by the unit caveat. The second sentence is slightly awkward in phrasing ('Unless a parameter says otherwise, lengths and coordinates are in cm') but nothing is wasted.

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 12-parameter, non-idempotent mutation tool with no output schema, the description covers mode and units but omits replacement semantics, error behavior, and any indication of what is returned. An agent can invoke it, but not fully predict its effects.

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 75%, so the schema documents most parameters itself, and the description's only addition is the repo-wide unit convention (cm/degrees). It does not clarify the near_x/near_y/near_z triple, the face_index tie-break, or valid thread_type/thread_class values beyond what the schema already says. Baseline 3 is appropriate.

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 ('Add threads to a cylindrical face') plus the two modes (cosmetic or modeled), which is more than the title alone. No sibling tool covers threads, so there is nothing to disambiguate from in the sibling list, which keeps it just short of a 5.

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?

Implicit guidance appears in the schema (near_x 'Instead of face_index', is_internal 'Omit it: it is inferred') but the description itself gives no when-to-use/when-not-to-use or alternative-tool routing. Adequate but thin.

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