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

With no annotations, the description carries the full behavioral burden, yet it only adds the payment/trial note ("5 free trial calls per signed wallet") — useful auth/pricing context, but nothing about determinism, numeric output, or input validation. Effects on malformed or non-numeric string coordinates are entirely unexplained.

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?

It is compact and front-loaded with no filler sentences, but the brevity comes from under-specification rather than discipline, and the second clause ("Distance between manhattan") is garbled enough to cost clarity. The emoji-flagged pricing note is clear and properly separated.

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?

A four-parameter geometry tool with no annotations, no parameter descriptions and no output schema gets only a tautological sentence plus a pricing note. Nothing an agent needs in order to call it correctly — coordinate ordering, numeric format, or result shape — is present.

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 description coverage is 0% for four undocumented parameters (x1, x2, y1, y2, all typed as string with no required fields), and the description supplies no meaning whatsoever. A caller cannot tell which pair forms the first point, whether order matters, or whether strings must be numeric.

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?

"Manhattan Distance: Distance between manhattan" restates the tool name and then circularly repeats it; the phrase is ungrammatical and never states that it computes the L1/Manhattan metric between two 2D points. An agent must infer the actual operation from the name alone, and nothing distinguishes it from siblings like x402-distance, x402-distance2d or x402-chebyshev-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 when-to-use guidance at all: no statement that x1/y1 is point A and x2/y2 is point B, and no pointer to alternative distance tools (Euclidean, Chebyshev, 3D) for other cases. The only non-computational sentence concerns billing, not usage selection.

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