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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, so the safety profile is covered. The description adds genuinely useful context those annotations cannot: cost (0.005 USDC per call) and latency (2000 ms p95). It does not cover auth/API-key needs or rate limits, so it falls short of 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?

Usage and exclusions are front-loaded, then cost/latency/category. Every sentence carries information, though a few clauses ('Returns JSON with an ENS lookup on Ethereum in one call') are slightly redundant against the existing output schema.

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, the description needn't explain return shapes, and it covers the details an agent still needs: use cases, exclusions, per-call cost, and expected latency. Nothing material for correct invocation is missing.

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 schema already documents name, address, texts, and response_format, including the mutually-exclusive 'send name or address, not both' rule. The description restates the semantic intent (name->address, address->reverse, record keys) without adding syntax or defaulting details beyond what the schema provides; baseline 3 is appropriate.

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/resource pair (resolve ENS names / reverse-resolve addresses / read ENS records) and explicitly distinguishes itself from registration and non-ENS naming (Solana SNS). An agent can select this tool without ambiguity among 30+ siblings.

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 gives explicit when-to-use triggers ('resolve an ENS name', 'reverse-resolve an address', 'read avatar and profile records') and explicit exclusions ('Do not use for registering or renewing names, or non-ENS naming such as Solana SNS'). Nothing is left to inference.

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