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

With no annotations, the description carries full responsibility for behavioral disclosure, and it discloses only the vaguest concept. It doesn't state the formula, output units (J vs eV), input expectations, or whether this tool performs a computation or returns a constant.

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 extremely short, but this is under-specification rather than conciseness; 'Photon Energy' and 'Energy of photon' are redundant with each other and the name. The sentence doesn't earn its place because it adds no new information.

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 physics calculation tool with no annotations, no output schema, and no parameters, this description is wholly inadequate. An agent cannot determine what inputs to provide or what value and units will be returned, making correct invocation impossible.

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 has 0 parameters, so per the baseline rule the description need not add parameter detail. However, the description also fails to clarify why zero params are appropriate for a physical quantity that typically needs frequency or wavelength, which slightly undermines the baseline score.

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 'Photon Energy: Energy of photon.' is a tautology that effectively restates the tool name. It identifies the topic but provides no verb or specific operation, and it does nothing to distinguish this tool from siblings like kinetic-energy or potential-energy beyond the name itself.

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?

No when-to-use guidance or exclusions are provided. The description doesn't mention that photon energy normally requires frequency or wavelength input, nor does it compare against related siblings such as x402-energy or x402-frequency.

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