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

Annotations establish the read-only, non-destructive, closed-world safety profile. The description goes beyond them by disclosing the response shape {valid, canonical, fingerprint} and a concrete pricing model: $0.002 USDC per successful call via x402, with failed calls uncharged. That cost/auth detail is exactly the kind of context annotations cannot carry. Minor gap: it does not say where the identifier comes from given the empty schema.

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?

Two dense sentences: the supported-type list first, then the return shape and pricing. Every clause carries information, with no hedging or repetition.

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?

Return shape, supported algorithms, cost model, and safety profile are all covered, which is more than most definitions offer. The one material omission is the input channel for the identifier, which is the single thing an agent must resolve before calling a zero-parameter tool.

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?

With zero parameters and 100% schema coverage, the baseline is 4, but the empty object schema creates a genuine ambiguity the description ignores: how is the single identifier passed? The enumerated validation methods (mod-97, Luhn, EIP-55) add domain value but do not resolve the invocation question.

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 states a specific verb (validate and canonicalize) and enumerates the exact resource types it handles, from email to EVM address. It is clearly distinguishable from siblings like normalize, hash, classify, and validate_json, which handle adjacent but different jobs.

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?

The enumerated identifier types imply when to reach for this tool versus validate_json or normalize, but the description never explicitly says so. It also omits the crucial guidance on how the identifier is supplied, given the tool takes zero parameters.

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