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

Beyond the readOnly/idempotent annotations, it discloses the multicall batching behavior, the paid x402 request flow and cost ($0.002 per call), the endpoint, and that bad input is refused before any charge. These are exactly the non-obvious operational traits an agent needs and annotations cannot convey.

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?

Front-loads purpose and scope, then payment mechanics, then the error guarantee, then the alternative. Dense but each sentence carries distinct information; only the pricing/URL sentence runs slightly long.

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 no output schema, the description still explains that the response includes the schema and an example, how to retrieve it (x402/MPP client), and the cost. For a paid data-proxy tool this covers everything needed to call it correctly.

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% and the enum is documented, so the schema already carries parameter meaning. The description names the supported chains but adds no format or syntax detail beyond what the schema provides, making the baseline 3 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?

States a specific verb+resource+scope: one ERC-20 balance for one wallet, reading balanceOf, decimals and symbol in a single multicall across five named chains. It also explicitly distinguishes itself from the sibling wallet_balance for multi-token/multi-chain 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?

Opens with the exact condition ('Use when you need one ERC-20 balance for one wallet') and closes with an explicit alternative and its trigger ('for several tokens or chains at once use wallet_balance'). When-to-use, when-not-to-use, and the alternative are all stated.

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