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

With no annotations, the description carries the full behavioral burden. It does add two genuinely useful facts beyond the schema: the accepted material set and the cost model ('1 credit per call'). It omits what happens on invalid material/kind, which fields are required per mode, and the result format, so disclosure is partial.

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 purpose sentence is front-loaded, followed by a dense, notation-style per-kind spec with no filler sentences. It is cryptic in style but every clause carries parameter information.

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 six-mode calculator with no output schema, no annotations, and a nested schema with zero description coverage, the input side is well covered but the description says nothing about the returned results, output units, or validation errors. Cost is the only operational detail supplied, leaving a real gap on the output side.

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 coverage is 0% and 'values' is an untyped nested object, so the description does heavy lifting by listing the exact keys per kind (length_mm, load_N, torque_Nm, etc.), the support/mode enums, and the valid material strings. It still does not state types, defaults, or whether every listed key is mandatory, so it compensates well but not completely.

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 names a concrete verb+resource ('engineering checks') and then enumerates the six calculation modes (beam, torsion, bolt, motor, spring, belt) with their inputs, so an agent knows exactly what this tool computes. It is distinguishable from CAD-construction siblings like cad_part or cad_build, though it never explicitly contrasts itself with them.

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 mode enumeration implies when each calculation applies (beam bending, bolt loading, motor sizing), which is implicit usage guidance. However, there is no explicit when-to-use, when-not-to-use, or named alternative among the many sibling calculators and CAD tools, so the agent must infer context.

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