What Material Data Is Held

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

With no annotations, the description carries the burden and does so by disclosing the reference's limits: no design allowables, no fatigue data, no high-temperature data, limited to typical values for common metals and plastics. It does not explicitly state that the call is read-only and side-effect free, but zero parameters and the 'list' framing make that inference safe.

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?

Three sentences, front-loaded with the core behavior and followed by the trigger condition and the scope limits. Every sentence adds distinct information — none restates the title or the empty 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 a zero-parameter tool with an output schema and no annotations, the description supplies exactly the missing pieces: what domain the reference covers and where its coverage stops. Return-value formatting is covered by the output schema, so nothing an agent needs before calling is absent.

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?

Zero parameters, so the baseline of 4 applies; there is nothing for the description to disambiguate. The description correctly avoids inventing parameter semantics for a tool whose schema forbids any input.

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 ('List what the material reference holds and what it does not'), which immediately separates it from the sibling material_properties tool that returns actual values. An agent can tell what it gets back without opening the schema.

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 two concrete triggering conditions — 'when a material was not found' and 'before promising a property' — with the explicit rationale that a gap should be visible rather than assumed. This is genuine when-to-use guidance tied to the surrounding tool set.

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