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

Annotations already cover read-only, idempotent, non-destructive, open-world, so the description adds real value by disclosing cost ($0.001 per call), accepted payment assets (USDC on Arc/Base/Solana, XNT on X1), and that the purchase completes inside the second call. The paywall behavior is the critical trait an agent must know. It stops short of describing failure modes (e.g., unpaid call returns terms, insufficient payment, unsupported token).

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 the capability and outputs in the first sentence, then the payment mechanics. Nearly every clause earns its place; the payment sentence is dense but necessary for correct invocation.

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?

No output schema exists, yet the description enumerates the returned fields (raw balance, decimals, symbol, unit balance, block), and the payment cycle is fully described. Minor gaps remain: no guidance on unsupported tokens or on what a payment-less call returns structurally.

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%, so chain, token, address, and payment are already documented. The description's only genuine addition is explaining the workflow around `payment` (obtain terms in a payment-less call, then submit the signed payload), which the schema only partially conveys. Baseline 3 is appropriate since the schema does most of the work.

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 ('ERC20 token balance of any wallet'), enumerates the supported chains, and lists the exact outputs (raw balance, decimals, symbol, token units, block read). This distinguishes it from the native-coin sibling evm_wallet_balance and the multi-token sibling evm_balances_bulk without needing their schemas.

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?

Gives an explicit two-step procedure: call once without `payment` to get terms, sign with your own wallet, call again with `payment`. That is actionable invocation guidance not found in the schema. It does not, however, state when to prefer this over evm_balances_bulk or evm_token_info for multi-token or metadata queries.

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