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

With no annotations, the description adds useful behavioral context: exact formulas, reference points, step-by-step working, and a per-call x402 price. It still does not describe return shape, rounding behavior, validation errors, or other operational details.

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?

The description is short and front-loads the core conversion purpose. The second sentence is awkwardly worded, but the overall structure is efficient and does not waste space.

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 simple three-parameter converter with no output schema, the description covers purpose, output flavor (formulas and steps), and payment terms. It is largely complete, though it could specify the return value more explicitly.

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%, so the from/to enums and value parameter are already documented in the schema. The description adds that conversions work both ways and mentions the units, but does not supply parameter syntax or constraints beyond 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?

The description clearly names the resource and operation: converting among Celsius, Fahrenheit and Kelvin. It is distinguishable from sibling converters by temperature domain, though it does not explicitly contrast with alternatives.

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?

It provides an implied usage condition: 'Use this when an agent needs to celsius, Fahrenheit and Kelvin, both ways.' However, the sentence is malformed and gives no when-not guidance or alternative tools to use.

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