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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the description's 'reads or computes only and changes nothing' is largely redundant. It does add genuinely new context beyond annotations: malformed addresses return 400 at no charge, calls cost $0.01 with 25 free, and repeats are billed because idempotentHint=false — but this billing detail is framed as generic pricing rather than explaining the non-idempotency.

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 purpose, units, and the sibling routing; the tail carries validation, pricing, and safety notes. Most sentences earn their place, though the pricing sentence ('$0.01/call via x402 USDC or a card key (/credits), first 25 free; failed calls free') is dense and only loosely tied to correct tool invocation.

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, the description must carry return semantics, and it does specify wei and MNT at the latest block, plus error behavior for bad input. It stops short of naming the response fields or shape, so an agent still learns the exact JSON structure only by calling it.

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?

The single address parameter is already 100% documented in the schema, so the baseline applies. The description adds meaningful behavior on top: malformed addresses are rejected with 400 without being charged, and a well-formed example address is given, which clarifies accepted format beyond 'string'.

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 resource (native MNT balance, eth_getBalance), the chain (Mantle), the block height (latest), and the units returned (wei and MNT). It also explicitly routes away from mantle_token_balance and wallet_portfolio, so the agent can distinguish it from the many sibling *_balance tools without opening a 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?

Gives a concrete use case ('check whether a wallet can pay gas or a transfer') plus two named alternatives with the conditions that select them (ERC-20 → mantle_token_balance, all holdings → wallet_portfolio). No inference about when to use it is left to the agent.

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