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

With no annotations, the description carries the full behavioral burden. It usefully discloses the paid x402 model and exact cost per call ($0.004 USDC on Base), which an agent must know before invoking, but it says nothing about return format, pagination relative to max_tokens, or behavior on unsupported/misspelled chains.

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 short sentences with zero waste; the core capability is front-loaded and the cost caveat follows. Every clause earns its place.

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 read-only tool with no output schema and no annotations, the description covers purpose and cost but omits return shape, ordering, and error semantics on invalid chains. Adequate minimum, but not complete for a paid multi-chain API call.

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 75%, so the schema already documents chain, tokens, and address. The description adds no parameter-level detail and is silent on max_tokens, the one undocumented parameter (default 50, max 200), leaving its pagination role unexplained.

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 a specific verb (fetch) and resource (ERC-20 token balances) scoped to a wallet on a chain, and credits the upstream provider (Alchemy Token API). It does not explicitly contrast with the close sibling cortex_aggregate_balances, so an agent must infer the single-chain vs. multi-chain distinction itself.

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?

The phrase 'for a wallet on a chain' implies the single-chain scope, which separates it from cortex_aggregate_balances, but there is no explicit when-to-use/when-not guidance or named alternative. Usage is only inferable.

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