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

The description discloses behavioral traits beyond annotations: it states 'Side-effect-free', explains validation via regex ('fast structured error vs capture-time stack'), and notes that orientation is not exposed. This adds value beyond the annotations (`readOnlyHint: false`, `destructiveHint: false`), and there is no contradiction.

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 fairly concise and front-loaded with the use case. It includes relevant technical details without excessive verbiage. Minor jargon could be reduced, but overall it is 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?

Given the complexity (6 parameters, output schema exists), the description is complete. It covers the return type (modified code + diagnostics), validation, binding references, constraints on sections, and the limitation about orientation. The output schema is mentioned implicitly by describing the result as a `Shape`.

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 100%, so the baseline is 3. The description adds meaning by explaining that `spine_binding` references an existing variable, `sections` must be strictly increasing in `t` and span [0,1], and that the result is a `Shape` for chaining. These details enhance understanding beyond the schema descriptions.

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 purpose: authoring a variable-section sweep along a spine. It specifies the action (insert a `variableSweep` declaration), the resource (`.kcad.ts` file), and the result (a `Shape`). The mention of chaining with `add_feature` differentiates it from sibling tools that handle other operations.

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 explicitly says 'Use this when you need to author a variable-section sweep along a spine' and provides context like inserting before the last top-level return. While it doesn't explicitly state when not to use, the context is clear. No direct alternatives are named, but the specificity implies this is for sweeps only.

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