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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds genuinely useful beyond-annotation context: the hard precondition of at least three non-collinear finite points, the deterministic nature of the normal, and the fact that it produces parameters rather than geometry.

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 trigger condition, then states outputs, then the exclusion and the precondition — a sensible order with no filler. The only minor waste is enumerating return fields that the output schema already covers.

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 single-parameter computational tool with full schema coverage, an output schema, and rich annotations, the description covers the trigger, the input provenance, the preconditions, and the scope boundary. An agent has everything needed to call it correctly without guessing.

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% and the single parameter is already documented as [x, y, z] triples in model units, so the baseline is 3. The description still adds meaning the schema cannot: the points must be finite and non-collinear, and they may originate from either scan data or mesh vertices.

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 (fit an orthogonal least-squares plane) against a specific resource (XYZ point-cloud data), and explicitly distinguishes itself from a surface-creation tool: 'Computes parameters only; it does not create a surface body.' An agent can tell this apart from siblings like add_surface or mesh_summary 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?

Opens with an explicit trigger condition ('Use this when you need to fit...') and clarifies input provenance ('points already parsed by the caller from scan data or mesh vertices'), which tells the agent this is not a scanner-reading tool. It does not name an alternative for when the agent actually wants a surface body, leaving that inference implicit.

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