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

With no annotations, the description must carry behavioral disclosure. It states the calculation rule (d2/162), the outputs, and unit support, which are useful. However, it does not mention side effects, whether it modifies data, error handling, or rounding behavior. For a calculation tool, read-only is implied but not stated, so a 3 is appropriate.

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 exactly two sentences with no redundancy. It front-loads the purpose and output, then adds the unit support note. Every word contributes to understanding, making it highly concise and well-structured.

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?

There is no output schema, so the description must convey what is returned; it does by listing total length, weight, and bars per tonne. It also specifies the input (list of rebar lines) and the rule. It lacks details on output formatting or edge cases, but for a straightforward calculation, it is sufficiently complete.

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 high (100%), with the lines parameter described as 'Rebar lines' and diameter_mm described with an example. The description adds value by clarifying support for both metric and US # sizes as diameters, which is not explicit in the schema. This enriches the meaning of the diameter_mm parameter, justifying a 4.

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 clearly states the tool's function: it performs rebar weight takeoff using the d2/162 rule, returning total length, weight in kg, and bars per tonne for a list of rebar lines. It also mentions support for metric mm and US # sizes, making it specific and distinct from the sibling calculator tools.

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?

The description implies usage for rebar quantity takeoff by describing the input and output. It does not explicitly exclude alternatives or name sibling tools, but given that none of the 36 siblings are rebar-related, the context is clear enough. It lacks explicit 'when to use' phrasing, but the purpose is self-evident.

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