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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It discloses none: no side effects, return format, units, limitations, error behavior, or processing semantics. It merely echoes the name, giving the agent zero knowledge about what invoking this tool actually does.

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 text is short, but this is under-specification rather than conciseness. The single sentence 'Distance2d: Distance2d' carries no information and earns no place, making it as unhelpful as a bare tool-name placeholder while failing to provide any usable content.

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?

With no annotations, no output schema, an empty input schema, and hundreds of overlapping sibling tools, a tautological description is completely inadequate. An agent selecting or invoking this tool has no way to know its purpose, required context, inputs, outputs, or relationship to similar distance functions.

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 properties and zero required parameters, so the 0-params baseline of 4 applies. There are no parameter semantics to explain; however, the description also fails to clarify how the tool obtains any coordinates or inputs, which is a notable omission given the tool presumably operates on some implicit data.

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 is a pure tautology: 'Distance2d: Distance2d' restates the tool name exactly and says nothing about what the tool does, what inputs it expects, or what it returns. An agent cannot determine that this computes 2D Euclidean distance, as opposed to any of the many distance-related sibling tools such as distance, distance3d, geo-distance, or manhattan-distance.

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, what problem it solves, or how it differs from the dozens of related measure/distance/computation siblings. The huge sibling list includes x402-distance, x402-distance3d, x402-geo-distance, x402-manhattan-distance, and x402-chebyshev-distance, yet the description provides no discriminating or routing information.

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