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

Annotations already cover readOnly/idempotent/non-destructive/openWorld, so the safety profile is settled. The description goes further by disclosing the cost model (25 free calls/day, then $0.01 USDC per call via x402) and a freshness discipline ('Never trust a remembered balance'), both of which are real behavioral context beyond the structured fields.

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?

Dense and waste-free: trigger, purpose, example, cost, and output pointer. The ordering is slightly inverted (usage precedes the statement of what the tool is), and the trailing 'Outputs explained: GET /api/tools/balance.' is an odd fragment, but nothing is padded.

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?

A two-parameter read tool with no nested objects and no output schema is well covered by trigger + purpose + example + cost. The only gap is return shape, which is gestured at via a docs URL rather than described, so an agent knows what to pass but not exactly what comes back.

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 the schema already documents both `wallet` and `network` (including the .sol-name exclusion and the devnet warning). The description only adds the inline example {"wallet": "<address>"}, which is marginal; baseline 3 is correct when the schema does the heavy lifting.

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: 'A wallet's SOL balance, read from the chain.' The 'SOL' qualifier implicitly separates it from sibling token-balance tools (tokens, token_account, find_token), so an agent can route correctly without opening schemas. No tautology, no vagueness.

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 strong prescriptive trigger ('Run before sending SOL or paying fees, to confirm the wallet has enough. Never trust a remembered balance.'), which is exactly the when-to-use context an agent needs. It lacks an explicit when-not or a named alternative sibling, so it falls just short of the top band.

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