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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds real behavioural context beyond that: two drawing formats produced, weight reported only conditionally ('where the site's calculator carries the size'), lap defaulting to the calculator's own value, and the explicit scope limit that it performs no design or code checking.

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 verb and scope, followed by an efficient output enumeration and a one-line boundary statement. The single long sentence listing outputs is dense but every item earns its place; no filler or repetition.

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 and the input schema is fully described, so the description does not need to explain returns or parameters. Given the tool's complexity it covers scope, outputs and the design/quantity boundary well; the only omission is any hint about default resolution between the redundant spacing vs lengthwise/widthwise count inputs.

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% across all 15 parameters, including nested lengthwise/widthwise/chairs objects and five enums, so the schema already carries the semantics. The description only loosely gestures at the inputs (bar size, spacing, cover, 'bars each way', lap) without adding format or edge-case detail beyond the schema, so baseline 3 applies.

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 ('lays out reinforcing bars in a rectangular slab or footing') and enumerates the concrete outputs: bars each way, bar lengths, total length with lap, stock sticks, weight, SVG and DXF. The closing boundary ('a quantity layout, not a design: it does not size structure or check a code') cleanly separates it from calculate/design-oriented siblings.

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 gives a clear exclusion ('not a design... does not size structure or check a code'), which tells the agent when this tool is the wrong choice. However, it never names the alternative to use instead (e.g. calculate or create_drawing), so routing is implied rather than explicit.

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