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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the description's job is to add operational context—which it does by describing chart contents (LPI sweep with alignment marks), the requirement to print at 100% scale, physical evaluation with the lens sheet, and the output ('image plus measurement instructions'). This goes well beyond what the safety annotations convey.

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?

Four sentences, each earning its place: purpose, usage triggers, chart/output description, and scope exclusion. Information is front-loaded so an agent can decide quickly, and there is no redundant restatement of the name or schema.

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 an image-generating tool with no output schema, the description carries the needed burden by stating that it outputs an image plus measurement instructions and requires 100% scale printing. Combined with fully documented parameters and clear scope boundaries, an agent has everything needed to select and invoke it correctly.

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%, and each parameter's meaning, defaults, and ranges are already well documented in the schema. The description reinforces that lpi is the nominal center of the sweep and implies sweep granularity via steps, but adds no syntax or format detail beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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 ('Generate a printable LPI pitch-test chart') and immediately distinguishes its purpose from siblings by explaining it measures/calibrates physical lens pitch. The scope sentence explicitly excludes print dimensions, view counts, and prices, which further separates it from calculate_output_params and get_print_quote.

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 names the triggering conditions: user has a nominal LPI and wants to verify the real value, calibrate a new sheet, or determine correct pitch before interlacing. The scope exclusion ('physical lens calibration only') provides clear when-not guidance against adjacent calculation and quoting tools.

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