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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered; the description adds genuinely non-structured facts: the exact price ($0.001 USDC on Base via x402) and that the response includes avatar records. It omits what a failed resolution returns (null vs error), which keeps it below a 5.

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?

A single dense sentence that front-loads both forward and reverse behavior, then appends the return-detail and pricing facts. No filler and no repetition of the title.

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 two-parameter, read-only lookup with no output schema, the description covers both directions, the return payload includes avatars, and the payment model is disclosed. The remaining gap is behavior when both or neither optional parameters are supplied, which the description leaves undefined.

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 100%, so the baseline is 3. The description adds only a little beyond the schema — the example names and the word 'primary' for reverse results — without explaining precedence when both name and address are provided.

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 pair of verbs (resolve / reverse-resolve) on a specific resource (Basename or ENS name ↔ Base/Ethereum address), which is enough to know exactly what the tool returns. It does not differentiate itself from the sibling base_address, which plausibly overlaps in scope, so it falls short of a 5.

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 description makes the two usage modes clear (pass a name for forward lookup, an address for reverse lookup), and the schema labels address as an 'Alternative'. However, it never says when to pick this over the sibling base_address, nor what happens if neither parameter is supplied despite zero required parameters.

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