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

Beyond the annotations (readOnly, idempotent, openWorld, non-destructive), the description discloses the data source (Base RPC), the payment model ($0.02/call via x402 on Base), the auth alternatives (prepaid x-credit-token header for unlimited calls, or 1 free call/day), and that no API key is required. This is exactly the operational context an agent needs before calling a paid endpoint.

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 core capability and its outputs are front-loaded in the first clause, followed by use case, input requirement, and pricing/auth in descending priority. Every sentence carries distinct information with no filler.

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?

An output schema exists, so return-value documentation is not required, and the description still previews the key returned fields. Combined with the explicit input requirement and the pricing/auth details, nothing an agent needs to invoke this tool correctly 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?

There is a single parameter with 100% schema description coverage, and the description only restates that address is the required input ("Required input: address"). No format hints (hex vs ENS), chain qualification, or validation rules are added beyond the schema, 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 states a specific resource (any Base address) and enumerates concrete outputs: EOA vs contract classification, ETH + USDC balance, transaction count, and activity level. That field-level detail makes it distinguishable from generic siblings like address_label or address_check. It stops short of naming or contrasting an explicit sibling, so it is clear but not fully differentiated.

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?

"Useful for counterparty and wallet checks" gives an implied use context but names no alternatives (e.g., address_trust, address_label, counterparty_check) and states no exclusions or prerequisites. Usage is inferable from the described outputs rather than explicitly guided.

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