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

With no annotations, the description carries the full burden of behavioral disclosure. It only says the value is a constant, providing no information about output units, precision, or representation. This is not actively misleading, but it is minimal.

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 definition is extremely short and front-loaded, but the leading 'Electron Mass:' prefix is redundant with the tool name and adds no value. The remaining phrase is concise but under-informative.

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 constant-returning tool with no annotations and no output schema, the description should clarify what value and units are returned. It only says 'constant,' leaving the exact output behavior, unit, and numeric representation unspecified.

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 zero parameters, so the schema fully defines the invocation surface. Per the zero-parameter baseline, the description's silence on parameters is acceptable and does not create a gap.

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 'Electron Mass: Electron mass constant.' restates the tool name without using an action verb such as 'returns' or 'retrieves'. It identifies the resource but is essentially tautological and does not distinguish this tool from other physical-constant siblings 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?

There is no guidance about when to use this tool versus alternatives, such as other mass constants or mass-conversion tools. In a sibling list with many similar constants, the agent is given no decision support.

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