Stoichiometry

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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered by structured data. The description adds the formula-requirement condition, but that same condition is also stated in the schema, and it doesn't say what happens if formula is omitted for a gram conversion (error vs default) or what precision the result carries.

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 short sentences, no filler, with the core capability stated first and the conditional rule second. Every sentence earns its place.

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 values need not be explained, and the input rules are fully covered by schema plus description. The only omissions are sibling routing and error behavior when a gram conversion is requested without a formula.

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% with enums on from/to, so the schema already documents every parameter. The description's formula rule merely repeats the formula parameter's schema description, adding no new syntax, format, or constraint information.

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 (convert) and an explicit domain resource set (grams, moles, particles), which distinguishes it from the generic convert_units sibling. It does not name a sibling or clarify its boundary against molar_mass, which also deals with grams/moles, so it stops short of full differentiation.

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 second sentence gives a clear conditional rule for when the formula argument is needed vs not needed, which is genuine usage guidance for a required parameter. However, there is no guidance on when to pick this tool over molar_mass or convert_units, and no statement of preconditions or failure modes.

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