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

Annotations already declare readOnly/ idempotent/ closed-world, so the safety profile is covered; the description adds value beyond them by describing what the response contains (line/band positions in nm, causal attribution such as Cr3+ in ruby, visual appearance) and naming its source. It stops short of stating response structure or whether the list can be empty for a given stone.

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?

One front-loaded sentence that describes the output first and attributes the source last; every clause (lines, positions, causes, appearance) carries information.

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?

With no output schema, the description usefully characterizes the return content, which is the main thing an agent needs for this simple single-enum lookup. Minor gap: nothing about response shape (list of entries) or behavior for a stone with no diagnostic lines.

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 coverage is 100% and the single parameter is an enum with a per-value description, so the schema does all the work. The description mentions 'one gemstone' but adds no constraint or semantics beyond what the enum already provides; baseline 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 concrete resource and scope: the absorption spectrum ('each absorption line and band') a hand spectroscope would show for one gemstone, with positions in nm and causes. That is specific enough to distinguish it from gem_properties (property lookup) and identify_gem (identification), even without naming them.

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?

Usage is only implied by the content ('what a hand spectroscope shows'), which suggests a reference-lookup task, but the description never says when to pick this over gem_properties or identify_gem, nor states any prerequisites or exclusions.

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