open_part

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

With no annotations at all, the description carries the burden well: it discloses the state change (becomes current part), the 30 MB import guard with the allow_large escape hatch, the 2-minute call limit risk, and what an import returns (solid body count, mass properties). It does not say what happens to an already-open part or whether the change is reversible, which keeps it below 5.

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?

Dense and front-loaded — the core action and state effect come first, with caveats after. The middle sentence is somewhat sprawling with nested parentheses and mid-sentence line breaks, costing a little readability.

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 no annotations and no output schema, the description covers the important ground: what the call does to document state, what an import returns, and the failure conditions. Only the effect on a pre-existing current part is unaddressed.

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 0%, so the description must compensate. It explains the non-obvious parameter ('an import over 30 MB unless allow_large=True'), which is the only ambiguity; 'path' is left undefined but the accepted file formats are enumerated in the opening sentence.

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 ('Open a .sldprt, or import a STEP/IGES/Parasolid file as a new part') plus the resulting state ('it becomes the current part'). This clearly separates it from new_part, open_assembly, and activate_document in the sibling list.

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 real usage context: list_features/list_dimensions show its history and dimensions, and 'a file holding an assembly is refused' implicitly routes assembly files elsewhere. It never names the alternatives (open_assembly, new_part, activate_document) explicitly, so the agent must infer the routing rather than being told.

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