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

Annotations already cover safety (readOnly, idempotent, non-destructive, open world), and the description adds value beyond them: live on-chain reads rather than cached data, plus pricing/rate-limit behavior (25 free calls/day, then $0.01 USDC via x402). The freshness warning is behaviorally important for a balance tool.

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-loads the most important guidance (run before spending) before purpose and parameters, and every sentence carries information. The inline parameter recap duplicates the schema, which is the only real waste; the docs pointer at the end is a reasonable close.

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?

Since there is no output schema, the description should ideally say what a successful read returns (units, e.g. lamports vs SOL) — that is the one gap. Everything else an agent needs (when to call, network default, cost, live-read semantics) is present.

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 both parameters are already fully documented, including the .sol-name exclusion and devnet-only guidance. The description largely restates the schema (wallet, network, mainnet default) without adding new syntax or format detail, so the 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 and resource: "Reads a wallet's SOL balance straight from the chain." The SOL specificity distinguishes it from token-oriented siblings like tokens, token_account, and find_token, so an agent can route correctly without opening the 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 an explicit trigger ("Run before sending SOL or paying fees") and a strong caution ("Never trust a balance remembered from earlier in a chat"), which is genuine usage guidance. It does not explicitly name sibling alternatives for non-SOL balance checks, so it stops short of a full 5.

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