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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description only needs to add context. It adds the content scope of a pattern record but says nothing about failure behavior when an identifier matches nothing, or about whether lookups are case-sensitive or slug-normalized.

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?

A single sentence with the verb and resource front-loaded and zero filler. It is efficient, though the trailing enumeration of returned fields crowds out any usage guidance that would have been more valuable.

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?

The tool is a simple single-record read, an output schema exists so return values need no explanation, and annotations cover safety. The remaining gap is guidance on how this relates to find_patterns and match_materials, which the description leaves unaddressed.

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?

All four parameters are optional with 100% schema description coverage, so the schema already carries identifier syntax, length limits, and examples ("cat or sunflower"). The description adds no meaning about which identifier form to prefer or why four aliases exist, leaving it at the high-coverage baseline.

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 ("Returns one library pattern") and enumerates the payload: size, colours, making steps, materials, and yarn quantities for two kit types. It does not name or distinguish itself from siblings such as find_patterns or get_material_guide, so an agent must infer the read-one-by-identifier role from the name alone.

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?

No explicit when-to-use statement, no prerequisites, and no routing to alternatives. The phrase "one library pattern" weakly implies it is the single-item lookup counterpart to a search tool, but that inference is left entirely to the agent.

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