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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety is covered. The description adds two useful behavioral facts beyond them: parenthesized group syntax is supported and the result is expressed in g/mol. It says nothing about invalid-formula handling or case sensitivity of element symbols.

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 sentence, front-loaded with the operation and capped by the unit of the result. Nothing padding, nothing restating the title verbatim.

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 an output schema, rich annotations, and a single well-documented parameter, the description covers what an agent needs to invoke it correctly. Minor gaps remain around input normalization (case, whitespace, hydrates) and error behavior.

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% and the schema already supplies examples (H2O, CO2, NaCl, Ca(OH)2), so the baseline is 3. The 'supports parentheses' note adds a real syntax constraint, but it partly duplicates the Ca(OH)2 example already visible in the schema.

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+resource: 'parse a chemical formula and compute molar mass in g/mol'. That is unambiguous and self-contained, though it does not differentiate itself from chemistry siblings such as calculator_moles, calculator_stoichiometry, or calculator_concentration.

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?

There is no when-to-use or when-not-to-use guidance and no named alternative. An agent must infer from the name alone that this is the formula-to-molar-mass tool rather than the moles, concentration, or periodic-table tools.

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