Convert any value between units of length, weight, volume, or temperature (e.g., km to miles, Celsius to Fahrenheit) to resolve unit-math errors in calculations.
Convert a value between units of length, weight, volume, or temperature (fixes LLM unit-math errors)
| Name | Required | Description | Default |
|---|---|---|---|
| value | Yes | ||
| toUnit | Yes | e.g. "mi", "kg", "fahrenheit", "l" | |
| fromUnit | Yes | e.g. "km", "lb", "celsius", "gal" |
Changes observed during successful MCP inspections.
v2.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the transparency burden. It communicates a non-destructive conversion operation, but it does not state the return format, failure behavior, or edge cases such as unsupported units or invalid values. This is adequate but not complete.
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?
A single dense sentence states the core action Fahrenheit and the reason to use the tool. It is free of redundancy and easy to scan, which helps an agent parse it quickly during tool selection.
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?
The description is enough for a simple unit-conversion call if the schema fills the gaps, but there is no discussion of valid unit spellings, output shape, or failure modes. Given no annotations and no output schema, an agent only obtains partial context about how to call the tool robustly.
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?
The input schema already supplies unit exampleshare and example unit strings, and the description adds the supported categories. However, it is not clear whether strings like '3.5m' are accepted, whether compound units work, or how flexible unit names are, leaving some guesswork for the agent.
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 uses a specific verb ('convert'), names the resource (a value), and narrows scope by listing length, weight, volume, and temperature. It naturally distinguishes this tool from siblings like convert_timezone or convert_base by stating the domain.
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 clearly implies when the tool should be used: whenever an agent needs to convert a value between physical units without doing error-prone arithmetic. It does not explicitly name alternatives or exclusions, but the category list makes the main usage context obvious.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.