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

Annotations already declare the safe read-only, idempotent, closed-world profile, so the bar is lower. The description still adds real behavioral context the annotations cannot: only 'active' materials are returned, and the price is defined as a gross 'price from' for a 50×70 cm rectangle with polished edge and no options in the shop currency, which pre-empts misinterpretation of the quoted figure.

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 compact sentences, front-loaded with what is listed and what fields come back, then the follow-up action. No filler and no repeated schema/annotation content.

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?

An output schema exists, so return structure need not be spelled out, and the description covers the non-obvious semantics of the returned price. What is listed and what to do with the slug are both stated; the only minor omission is noting that response language follows the locale parameter.

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 there is a single optional locale parameter whose enum values and shop/currency implications are fully documented in the schema. The description's mention of 'shop currency' loosely implies locale-dependence but adds no syntax or defaults beyond what the schema already provides, so the baseline of 3 applies.

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 ('Lists the active mirror and glass materials') and enumerates exactly what each entry carries: thickness, size limits in cm, and a gross 'price from'. It also routes the agent downstream by naming quote_mirror, so it is distinguishable from the sibling catalog tools.

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 clause 'Use the slug in quote_mirror' gives explicit sequencing: call this to discover materials, then feed the slug into the quoting tool. There is no explicit when-not or exclusion, but the workflow context is clear and actionable.

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