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

The description goes far beyond annotations by detailing pricing ($0.01/call, first 25 free), operational failure modes (400 uncharged for malformed address), and the nature of the computation (reads/computes only, no changes). This is essential operational context.

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?

While it is slightly lengthy due to the number of required operational details (pricing, failure modes, routing), it is well-structured. The most critical information (purpose, routing) is prioritized, leading to high utility.

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?

The definition is exceptionally complete, covering the functional intent, architectural constraints (read-only), operational constraints (cost, rate limits), and failure modes. No critical information needed for correct selection or 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?

With 100% schema coverage, the baseline is already high. The description adds value by providing a concrete example of a valid address and clarifying that the address must be a 0x wallet or contract.

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 precisely that the tool retrieves the native ETH balance of a 0x wallet address on the Base network. Furthermore, it clearly differentiates its function from related tools by directing users to `base_token_balance` and `wallet_portfolio` for specific needs.

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 definition provides excellent usage guidance by explicitly stating its intended use (checking gas payment capability or transfers) and providing clear alternatives for ERC-20 tokens and total holdings. This eliminates ambiguity for the agent.

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