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

With no annotations, the description carries the full burden and does disclose two non-obvious traits: a content policy exclusion ('Does not design weapons, firearms, ammunition or explosives') and a per-call cost ('Cost: 1 credit per call'). It also describes the return behavior (tool recommendation + extracted parameters). It does not cover failure modes for vague or unparseable ideas, which keeps it short of a 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?

Four short sentences, front-loaded with the action and an example, followed by the return shape, the exclusion, and the cost. No filler; each sentence carries distinct information the agent needs.

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 routing tool with no output schema and no annotations, the description covers input form, expected output, cost, and content limits. It leaves the ambiguity-handling path (what happens when the idea is too vague to map to a tool) unspecified, but otherwise an agent has enough to call it 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?

Schema coverage is 0% — the 'idea' property has no description, only minLength/maxLength constraints. The description compensates by explaining what belongs in the field (plain-language machine/mechanism/product description) and giving worked examples ('40 kg lift arm', 'a 30:1 gear reducer for a winch'), which tells the agent that numeric quantities should be embedded in the text so parameters can be pre-filled.

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?

The description names a specific verb and resource ('Describe a machine, mechanism or product idea in plain language') and pins down its distinct role among the cad_* siblings by stating it 'Returns which CAD tool to run and pre-filled parameters' — i.e. it is the router, not the builder (cad_build), calculator (cad_calc), or part/fusion tools. An agent can tell it apart from cad_machine/cad_part without opening 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?

Usage is only implied: because it 'returns which CAD tool to run', the agent can infer this is the entry point before cad_build/cad_machine. There is no explicit when-to-use/when-not statement and no sibling named as an alternative, so the routing guidance must be inferred.

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