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

With no annotations, the description carries the full load and does well: it discloses the pay-per-call billing model ($0.002 USDC on Base), that settlement only occurs on successful reads while invalid input/not-found/upstream errors cancel it, and that output includes both raw and decimal values plus the symbol. It omits anything about auth/payment-signature requirements (left to schema) and latency or rate limits.

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?

Two tight sentences: capability and scope first, then the mis-scaling rationale, then billing terms. Every clause carries information an agent or caller needs, and nothing is buried.

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, but the description still characterizes the return value (raw + decimal-formatted + symbol) and the error/billing behavior, which is the critical unknown for a paid read. It stops short of describing the error response shape or what happens for a non-contract token address.

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 100%, so all four parameters are already documented, including the chain list and 0x-prefix requirements. The description adds only the count of supported chains ("7"), which duplicates rather than extends the schema; 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 ("ERC-20 token balance of any address") plus scope (7 EVM chains) and return shape. The "ERC-20" qualifier implicitly distinguishes it from chain_native_balance and chain_token_info, so an agent can pick it without opening another 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?

Usage is implied by "any address on 7 EVM chains" and the pricing note, but it never says when to prefer this over siblings like chain_native_balance (native coin) or chain_portfolio (multi-asset). No exclusions or prerequisites are stated.

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