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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is fully covered and this pure-calculation tool needs little more. The description adds nothing behavioral beyond restating inputs/outputs, and its 'diameter mm' input does not exist in the schema, which mildly misleads rather than clarifies.

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 core computation followed by inputs and returns. The 'Use for jewelry shopping' clause and the list_bundles tangent add little but the text stays tight overall.

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?

An output schema exists, so return-value explanation is not required, and the description need not repeat 'Returns size in EU/US/UK/JP'. However, with two required params at 0% schema coverage, the description should document from_system semantics and reconcile the phantom 'diameter' input instead of leaving it ambiguous.

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 0%, so the description must carry parameter meaning. It does explain circumference_mm as millimeters but claims a 'diameter mm' input that is absent from the schema, and it never explains the required from_system enum or why FR maps to the advertised 'EU'.

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 ('Find ring size') with explicit scope (EU/US/UK/JP, from circumference or diameter). An agent can tell what it computes, though it never distinguishes itself from the sibling calculate_ring_size_convert.

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?

Only guidance is the vague 'Use for jewelry shopping' plus an irrelevant pointer to list_bundles for 'textile-mode' calculators. No when-to-use condition, no mention of the obvious alternative calculate_ring_size_convert, no prerequisites.

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