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

With no annotations, the description carries the full burden and does meaningful work: it discloses that reads are live from chain, that the call is a paid x402 endpoint costing $0.005 USDC on Base, and that output is decorated with symbol and decimals. It omits failure behavior (unverified tokens, payment rejection) and rate limits, so it falls short of a 5.

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?

A single dense sentence that front-loads the return value and ends with the cost caveat, with no filler. Slightly packed — the payment detail and formatting detail compete for one clause — but nothing is wasted.

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?

For a 2-parameter tool with no output schema, the description conveys what comes back (native balance plus per-token balances with symbol/decimals) and the commercial precondition (x402 payment). What's missing is error handling for tokens lacking metadata and any hint of response shape beyond formatting.

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 already document address format and the comma-separated, max-20 token contract list. The description's 'up to 20 ERC-20 tokens you list' restates the schema rather than adding new syntax, ordering, or edge-case guidance, so baseline 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?

States a specific verb+resource: returns native ETH balance plus up to 20 ERC-20 token balances for a wallet, read live from Ethereum, with symbol/decimals formatting. The chain qualifier 'on Ethereum' clearly distinguishes it from the arbitrum_/base_/polygon_/optimism_wallet_balances siblings.

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?

It implies usage (check a wallet's ETH and listed ERC-20 holdings) and notes the x402 cost, but never states when to prefer eth_wallet_profile or eth_token_snapshot, nor any prerequisite such as holding USDC on Base to pay. The alternative routing is left to inference.

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