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

No annotations are provided, so the description carries the full behavioral burden. It states the core operation but omits important behavior: what happens for a zero vector (division by zero), how precision/rounding is handled, whether it errors on non-numeric input, and no cost/auth detail beyond a free-trial note. For a math tool with zero annotation coverage this is a substantial gap.

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?

One tight sentence front-loads the operation and result, followed by a short trial/pricing note. The free-trial emoji line is marketing noise rather than tool semantics, but it is brief and does not bury the core definition.

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?

No annotations, no output schema, an undocumented string parameter whose encoding format is critical, and no mention of edge cases such as the zero vector or non-numeric input. For a numeric utility where input format determines whether the call succeeds at all, the definition is materially incomplete.

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% and the single parameter 'values' is typed only as a string with no description. The description says 'a numeric vector' but never explains how a vector is encoded in a string (comma-separated? JSON array? space-delimited?), nor does it note that the parameter is not marked required. With the schema contributing nothing, the description fails to compensate.

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 gives a precise verb-plus-operation ('divides a numeric vector by its Euclidean magnitude to return a unit vector'), which is far more informative than the bare name and implicitly distinguishes it from x402-vector-norm (which returns the magnitude). It does not, however, explicitly say how it differs from the many other 'normalize' siblings (x402-normalize, x402-normalize-array, x402-standardize, x402-min-max-normalize).

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 explicit when-to-use or when-not-to-use guidance is given. The stated mechanism (Euclidean magnitude, unit vector) implicitly separates it from min-max/standardization siblings, but an agent facing an ambiguous 'normalize this array' request has no stated rule for choosing this tool over x402-normalize-array or x402-standardize.

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