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

With no annotations, the description carries the full burden and does well: it declares the tool read-only, warns that diameters are model estimates rather than measurements, and lists the returned fields including diameter, construction label, resolved dTex, and version metadata. The only minor gap is that it does not describe error behavior for invalid basis/threadId combinations.

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?

The description is front-loaded with read-only status and purpose, then moves through usage, input conditions, caveats, and response contents in a logical order. It is slightly longer than necessary because it repeats parameter ranges already covered by the schema, but no sentence is seriously wasteful.

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 computational tool with no annotations and no output schema, the description explains the return payload, the estimate caveat, and the valid input combinations. An agent has enough information to invoke it correctly without needing to infer missing behavior.

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 description coverage is 100%, so the schema already documents all four parameters, including conditional requirements and ranges. The description reinforces the basis/threadId/dtex conditions and explains that threadsPerStrand 2 means the 2 × 3 construction, but these details are also present in the schema, so it adds little beyond structured data.

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 uses a specific verb and resource: it calculates the estimated diameter of a three-strand rope from thread linear density and threads per strand. It clearly distinguishes the tool from the sibling find_rope_threads, which solves the inverse problem.

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?

It explicitly states when to use the tool: when the user asks how thick a rope will be or what diameter a custom dTex produces. It also states when to use the alternative: find_rope_threads when the user wants threads for a target diameter.

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