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

Annotations already declare readOnlyHint and openWorldHint, and the description adds meaningful behavioral context by mentioning a specific payment requirement and recipient. However, the phrasing 'Paid $0.01 USDC exact on Base' is ambiguous about whether payment is required beforehand, who pays, or how the payment mechanism works.

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 description is concise, packing the returned fields and a payment recipient into two short sentences. However, the most important functional content is not front-loaded; the payment clause appears first, making the structure slightly awkward for an agent scanning for purpose.

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?

For a one-parameter tool with no output schema, the description usefully lists the four returned data points (isContract, ETH balance, USDC balance, tx count). Still, it lacks clarity on the payment prerequisite and invocation flow, and provides no response shape or broader usage context, so it is only minimally complete.

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?

The schema already provides 100% coverage for the single address parameter, including format and chain details. The description merely repeats 'for an address' and does not add new parameter-level constraints, defaults, or edge cases beyond what the schema documents.

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 specifies the tool returns on-chain metrics for an address (isContract, ETH balance, USDC balance, tx count), which is more specific than the bare name 'who' and distinguishes it from sibling tools like sanctions or domain. It lacks an explicit verb such as 'returns' and buries the core purpose behind a payment clause, but the functional intent is still clear.

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 guidance on when to use this tool versus alternatives such as check, email, or sanctions. The description simply says 'for an address' with no conditions, exclusions, prerequisites, or mention of alternative tools, leaving the agent to infer appropriate usage.

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