units.convert

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

Beyond the readOnly/idempotent annotations the description discloses real behavioral traits: dimensional mismatch or unknown units raise an error, and the output magnitude is a string that may use exponent notation such as 1E+3. It stops short of describing any rounding behaviour for the general case, but given an output schema exists this is solid disclosure.

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?

Four compact sentences, each contributing something distinct: purpose, parameter formats, error condition, output format, and the temperature reroute. Nothing is repeated and the most decision-relevant content comes first.

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 three-parameter read-only converter with an output schema, the description covers input formats, failure modes, output quirks, and the one dangerous alternative. Nothing an agent needs in order to invoke it correctly is missing.

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?

With 0% schema description coverage the description carries the full burden and does so: magnitude is a Decimal string, from_unit and to_unit are pint unit names with concrete examples (meter, foot, km). All three parameters gain meaning not present in the bare schema titles.

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 names a specific verb and resource (physical unit conversion via pint) and explicitly distinguishes itself from units.temperature for Celsius/Fahrenheit. An agent can tell exactly what this tool does and which sibling handles the temperature edge case.

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 gives one explicit exclusion: use units.temperature for Celsius/Fahrenheit because of trailing-digit rounding. It does not address the other unit-specific siblings (units.pressure_convert, units.energy_convert, units.data_size_convert, units.time_small_convert), leaving the agent to infer which converter handles which dimension.

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