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

Annotations already cover read-only, idempotent, open-world, non-destructive, but the description adds material context beyond them: exact pricing ($0.03/call via x402 on Base), the prepaid x-credit-token header for unlimited calls, the absence of a free tier, and that no API key is required. It also cautions that identity is a signal, not proof of honesty, which is genuinely useful behavioral framing.

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 lead question is front-loaded and immediately scannable, and each subsequent clause adds a distinct fact (mechanism, output, pairing, pricing). It is dense and slightly long, but no sentence is filler, so it lands just under a 5.

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 an output schema present, return values need not be spelled out, and the description still summarizes the verdict shape. Combined with pricing, auth mechanism, and the honesty caveat, an agent has everything needed to call it correctly and interpret the result.

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?

There is a single parameter with 100% schema description coverage, so the schema already documents 'address'. The description's 'Required input: address' only restates the schema's required field and adds no format, chain, or validation detail, so the baseline of 3 applies.

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 names a specific verb and resource — a Coinbase-verified-vs-anon/sybil verdict plus Basename for an address — and pins down the mechanism (EAS attestation by verifications.coinbase.eth) that separates it from generic siblings like address_check, address_label, or address_intel. An agent can tell exactly what this returns without opening the schema.

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?

It frames the use case sharply ('the who am I dealing with? check for agents') and tells the agent to pair it with sign-guard/spend-audit for a full pre-transaction gate, which is explicit routing guidance. It lacks a when-not-to-use statement (e.g., versus counterparty_check or address_intel), so it stops short of a 5.

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