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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, but the description adds material context they don't carry: $0.01 per call via x402 USDC or card key, 25 free calls, failed calls free, malformed addresses rejected with 400 and uncharged, and repeats are billable. That pricing and error-handling profile is exactly what an agent needs before calling a paid endpoint.

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?

Purpose and scoping come first, followed by routing alternatives, then error and cost behavior — a sensible front-loaded order. It is dense but nearly every clause carries information; the ending slightly restates the charging model ("each call is charged, so repeats are not free") already implied by the pricing sentence.

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 one-parameter read tool with no output schema, the description covers return values (wei and BERA), the block height read, failure modes, and billing. Nothing an agent needs to invoke it correctly is missing.

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% for the single address parameter, so baseline is 3. The description adds a canonical example address and clarifies the rejection behavior for malformed input, which slightly exceeds what the schema states.

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 specific verb+resource ("Native BERA balance") scoped to a chain, a unit (wei and BERA), a block (latest), and an underlying RPC method (eth_getBalance). It explicitly distinguishes itself from bera_token_balance and wallet_portfolio, so an agent can route correctly without opening sibling schemas.

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 states the concrete use case ("check whether a wallet can pay gas or a transfer") and names both alternatives with the condition that selects each: ERC-20 tokens go to bera_token_balance, all holdings at once go to wallet_portfolio. That is explicit when-to-use plus when-not-to-use.

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