chain_balance

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

Annotations already declare read-only/idempotent/open-world, and the description adds real context beyond them: redundant RPC sourcing, the wei-plus-formatted return shape, and the x402 payment flow — including that an HTTP 402 with payment_required is a price quote rather than an error, which prevents an agent from misreading a non-failure.

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?

Front-loaded with the core purpose and tightly organized (example, usage, behavior). There is mild redundancy — the first sentence already implies the 'Use when' restatement of chains and tokens — but the payment caveat earns its space.

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, yet the description states the return format (wei plus formatted units), the chains, the inputs, and the auth/payment outcomes. An agent has everything needed to call it and interpret results correctly.

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 the baseline is 3; the description earns an extra point by naming the supported chain values, the default (base, also in schema), and providing a concrete example call with both parameters populated. It stops short of adding format constraints beyond the schema.

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 (native-token balance) plus the supported chains and input types (address or ENS). It also explicitly distinguishes itself from siblings chain_token_balance and wallet_portfolio, so an agent can route 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?

"Use when you need the native-token balance... Not for token balances (use chain_token_balance) or a full holdings view (use wallet_portfolio)" gives explicit when, when-not, and named alternatives. Routing is fully determined.

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