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

Annotations already declare read-only, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds genuinely new operational facts: public RPC dependency, a per-successful-call price of $0.005 USDC via x402 on Solana, and an equivalent HTTPS endpoint. It does not describe failure/refund behavior when a call fails, which is the one notable gap for a paid tool.

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?

Four tight sentences, front-loaded with what is returned and where, followed by the token-count limit, the read-only note, and pricing. The bare URL at the end is slightly tacked on but still earns its place as an alternate access path.

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 carries return-shape duty, and it does say balances are returned per native ETH and per ERC-20 token across the chosen chain. It stops short of describing result structure or how zero balances appear in the response, which would matter since include_zero defaults to true.

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 baseline is 3. The description still adds information the schema lacks: the cap of 20 token contracts and which tokens constitute the 'major' default set (USDC, USDT, WETH, DAI/ARB), which materially affects what an agent should pass.

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?

Names the specific verb+resource (native ETH and ERC-20 token balances for an address) and constrains scope to three named chains. It is clearly distinguishable from evm_token_transfers, evm_read and wallet_risk_basic without opening a schema.

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 real usage context: omit tokens for the default set, pass up to 20 contracts, chain defaults to eth. But it never names an alternative sibling (evm_read, evm_token_transfers, sol_balance) or states when a caller should prefer those instead, so the routing guidance is implied rather than explicit.

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