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

No annotations exist, so the description carries the full burden. It usefully discloses cost ($0.001 USDC), historical-block support, and an example return shape (balance, balance_wei, block), but says nothing about payment/auth mechanics, rate limits, or error behavior for an invalid address or unknown block.

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 core purpose is front-loaded in the first clause, and the example input/output is compact and information-dense. The trailing '$0.001 USDC. Related: ... $0.003.' fragment is slightly staccato and partially duplicates the /wallet mention, but no sentence is wasteful.

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 and no annotations, the description does the heavy lifting: it states the RPC source, the optional historical block, an example call/response, and cost, which is enough to invoke correctly. The only real hole is the undocumented 'wallet' parameter and the absence of any error/auth context.

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 0%, so the description must compensate, and it partially does: address ('any address'), block (optional, historical), and chain (example 'ethereum'). The fourth parameter, 'wallet', is never mentioned anywhere, leaving its meaning and relationship to address entirely undocumented.

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?

The description opens with a precise verb+resource: 'Native coin balance (ETH/POL) of any address via eth_getBalance, optionally at a historical block.' It names the underlying RPC method and scope, which cleanly separates it from chain_erc20_balance, chain_erc1155_balance, and wallet_balances without the agent needing to open any 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?

It explicitly routes the agent elsewhere with conditions and prices: '/wallet ($0.003) for native + major tokens in one call' and 'Live native+custom ERC20s: /chain/live-balance $0.002'. The alternative and the condition that selects it are both stated rather than inferred.

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