start_sketch

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

Annotations already declare non-read-only, non-idempotent, non-destructive. The description adds only the implicit state dependency (a plane or face must already be selected), with no mention of failure behavior when nothing is selected or whether an in-progress sketch is affected.

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?

A single front-loaded sentence with no filler. Nothing could be removed without losing information.

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 zero-param initiation tool with annotations and an output schema, this is roughly adequate, but it omits the selection prerequisite, error conditions, and the natural follow-on (sketch_* / end_sketch), which an agent would need to chain this correctly.

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?

Zero parameters, so the baseline is 4. The description does usefully note that the target comes from the current selection rather than an argument, which explains why the schema is empty.

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 ('Opens a new sketch') plus the target context ('selected plane or face'), which distinguishes it from end_sketch and the sketch_* drawing primitives. It stops short of naming a sibling explicitly, so an agent must infer the boundary itself.

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?

Implies the prerequisite via 'selected plane or face' but never says to call select_plane / select_face_at_point first, nor when to prefer this over new_part or other construction entry points. Usage is inferred rather than stated.

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