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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds real behavioral value beyond that: parts are parametric and datasheet-dimensioned with authentic footprints/hole patterns, and it names the op used to consume a result. It stops short of describing return shape or pagination.

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 resource and its contents, then the insertion path and the usage nudge. Four short sentences, each earning its place, though the closing line leans slightly promotional.

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 simple read-only, parameterless-required browse tool with full schema coverage and full annotations, the description covers what it lists and why it matters. It could say a bit more about the returned item fields, but no output schema exists and the gaps are minor.

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 `search` and `category` are already documented. The description only implicitly touches parameter semantics by listing content categories, which hints at valid category values but adds nothing concrete. Baseline 3 applies when the schema does the heavy lifting.

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 resource (the built-in part library OwlCAD ships) and enumerates its contents (brackets, fasteners, spacers, reference bodies, mechanism pieces). This clearly separates it from the list_projects/list_folders siblings, which browse user content rather than the built-in library.

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 a clear trigger ('Reach for this before hand-modelling something that sounds standard') and routes to the follow-up action (insert via an edit_project `addPart` op). No explicit when-not/alternative exclusions, but the context is unambiguous.

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