construction_axis

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

With no annotations, the description carries the full burden and does so: it discloses the two distinct failure modes (INVALID_PARAMS with a structured details payload for wrong entity kinds, FUSION_API_ERROR for unbuildable geometry) and states that a failed build leaves the timeline unchanged. It also spells out the return payload inline, so the agent knows what it gets back.

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 action, then a compact table for the branching logic, then error behavior, then two concrete call examples. Dense but every block carries distinct information; no sentence is redundant with the schema.

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 9-parameter tool with one required discriminator, no output schema, and no annotations, this covers everything an agent needs: method selection, ref syntax, failure semantics, mutation-on-failure guarantee, and return shape. There is no meaningful gap left.

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 100%, so baseline would be 3, but the description adds something the schema structurally cannot express: the per-method field requirements in the table, including how many points 'two_points' needs and the constraint that the 'perpendicular_at_point' point lies on the given face. It also documents the ref-string vocabulary and points at inspect_query for deriving face refs.

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?

Opens with a specific verb+resource ('Create a construction axis') and immediately names the downstream consumers (revolve, circular patterns, joints). An agent can distinguish this from construction_plane and construction_point without inspecting either 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?

The method table is effectively a decision guide: it tells the agent which geometric situation maps to which method (two points, straight edge, cylindrical face, face+point, two planes). What is missing is sibling-level routing — nothing says when to reach for construction_plane or construction_point instead — so it stops short of explicit when-not guidance.

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