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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds real behavioral context beyond that: the result is delivered as a tool result, and owlcad://schema/primitives behaves differently with and without `keys` (index vs full ranges). It does not describe output format or size limits, keeping it below a 5.

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 the core purpose before the parameter nuance. Every clause carries information an agent needs — the fallback rationale, the URI scope, and the keys behavior — with no filler.

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 read-only reference reader with no output schema, the description covers purpose, selection condition, and the one non-obvious parameter behavior. It omits what the returned content looks like (structured vs prose) and any size considerations, a minor gap rather than a blocking one.

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% and the `keys` parameter already documents its primitives-only scope, so the baseline is 3. The description adds genuine meaning by contrasting the no-keys case (an index) with the with-keys case (full parameter ranges of named entries), which the schema does not spell out.

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 (reads an owlcad:// resource) and immediately clarifies the mechanism: it returns the resource as a tool result rather than via native MCP resource reads. This differentiates it from every sibling tool, none of which expose schema/reference content.

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?

Gives an explicit selection condition — use it when the client does not let you read MCP resources natively, and any owlcad:// URI referenced by other tools works here. It stops short of stating the inverse preference (use native resource reads when available), so it is clear context rather than full when/when-not routing.

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