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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's job is to add method and limits — and it does: results are interpolated between complete finite-element designs and calibrated against published designs, and it is a pre-design estimate. That is real behavioral context an agent could not infer from the annotations. It stops short of stating accuracy bands or how the range is derived.

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?

Two sentences, front-loaded with purpose and scope, then outputs, then method, then usage caveat. No filler and nothing buried.

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 carries the return-value burden and does so thoroughly — it lists every component of the result including the per-part breakdown and typical member sizes. Combined with the fully documented input schema and read-only annotations, an agent has everything needed to call and interpret it.

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%, including ranges, units and the roof-load relation (0.8 sk), so the schema already does the parameter work. The description only repeats the span range and adds no syntax or default guidance (e.g. when to choose rod vs tube bracing) beyond what the enum already conveys.

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 — steel tonnage estimate for a single-span pitched portal frame, span 15-30 m — and enumerates exactly what is returned (total tonnes, kg/m2, range, weight by part, member sizes). The only gap is that it does not distinguish itself from the sibling analyze_frame, which an agent might reasonably consider for a frame-related task.

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?

Explicitly says to use it for budgets, tenders and feasibility, and explicitly says when not to rely on it: 'a real design needs the actual loads and code.' That is a clear when/when-not framing, though it never names an alternative tool for the design case.

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