list_materials

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the description need not restate safety aspects. The description adds the qualifier 'compact' and 'summary', hinting that the output is a condensed representation rather than full material details. However, it does not disclose other behavioral traits such as ordering, filtering, or handling of empty sets.

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 a single, concise sentence of six words: 'Return a compact material summary.' It is front-loaded with the purpose and contains no filler or redundant information, making it an excellent example of brevity.

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 that the tool has no parameters, is marked read-only and idempotent, and has an output schema available, the description adequately covers the core purpose without needing to explain return values. The term 'summary' is slightly vague, but the output schema would clarify the exact shape, so the description is sufficiently complete for a simple list tool.

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?

The tool has zero parameters, so the schema coverage is trivially 100% and there is nothing to document. According to the rubric, a baseline of 4 applies when there are no parameters, and the description correctly requires no parameter details.

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 'Return a compact material summary' clearly identifies the verb (Return) and resource (material summary), and the tool name 'list_materials' reinforces this purpose. It is distinct from sibling list tools (list_members, list_phases, list_objects) by focusing specifically on materials, but it does not explicitly differentiate its behavior or scope.

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 provides no guidance on when to use this tool versus alternatives like list_objects or create_material, nor does it mention prerequisites or context. It is a minimal statement with no usage direction.

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