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

Adds substantial behavior beyond annotations: exact pricing ($0.01/call, $0.005 per extra country), the x402/USDC-on-Solana payment path, the _meta["x402/payment"] retry convention, and an HTTP fallback. Annotations cover safety flags but say nothing about cost or the two-step payment dance, which the description supplies.

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?

Front-loads the purpose in the first clause and then packs price, payment mechanics, and HTTP equivalent into two more sentences with no filler. Dense but every sentence carries operational weight.

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?

There is no output schema, yet the description never indicates what a verification verdict looks like (normalized address? deliverability flag? per-country results?). Payment and endpoint details are complete, but return-value expectations and sibling disambiguation are missing for a paid tool with a nested-object input.

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 coverage is 100%, so the nested address object and country/countries parameters are already fully documented in the schema. The description only echoes the 1-4 country limit and omits the 'supply either country or countries, not both' exclusivity that the schema carries. Baseline 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?

States a specific verb and resource ('Verify an address') plus scope ('in 1-4 countries'), so the action is unambiguous. It does not, however, distinguish itself from nearby siblings such as address_bundle, address_leg_us, or address_leg_nl.

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?

Gives clear operational guidance for the payment flow (call without payment to receive the PaymentRequired challenge, then retry). It never says when to choose this over address_bundle or the single-leg address tools, leaving sibling selection to inference.

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