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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, yet the description still adds substantial behavior an agent could not infer: zero balances are flagged explicitly, non-balanceOf addresses return found:false, plus x402 pricing ($0.002), the prepaid x-credit-token header, the 1 free call/day tier, and no API key requirement.

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 purpose and unique zero/found:false semantics are front-loaded, and each sentence carries information. It is on the long side and the payment/logistics sentence could be tightened, but nothing is redundant with the structured fields.

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, yet the description still covers the semantics an agent most needs: units (raw + decimals), resolved symbol/decimals, the explicit zero flag, and the found:false failure mode. For a two-parameter read on Base, nothing material 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 coverage is 100% and both parameters are documented in the schema, so the baseline is 3. The description only restates the two required inputs ('token, wallet') without adding format, expected casing, or chain-qualifier semantics beyond what the schema already provides.

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 precise verb+resource ('One wallet's balance of one token') plus chain scope ('ERC-20 balance on Base') and the exact shape of the answer (raw units, decimals, symbol). The 'one wallet / one token' framing implicitly separates it from aggregate siblings like wallet_tokens or token_info without ambiguity.

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 establishes the scenario (single wallet, single token, on Base) and lists required inputs and payment mechanics, but never names a sibling or states when NOT to use it, e.g. when to prefer wallet_tokens for a full portfolio. Usage is implied by scope rather than explicitly routed.

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