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

Explains the non-obvious annotation choice directly: 'not marked read-only because each call is charged,' which resolves the apparent tension between readOnlyHint=false and a pure read tool. It also discloses auth paths (x402 USDC or card key), pricing ($0.003/call, first 25 free), and that failed calls are free — behavior an agent cannot infer from the schema or annotations.

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 resource and return contents, then use cases, then example, then billing/auth caveats — a sensible information hierarchy with no filler. It is dense, and the pricing/auth sentence is arguably metadata rather than call guidance, but it is materially useful for deciding whether to invoke the tool.

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 carries the return-value burden and does so by listing the exact fields returned. Combined with address format, use cases, cost, and auth, an agent has everything needed to call and interpret this 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% and the single parameter is already documented with the same address-type notation, so the schema does the heavy lifting (baseline 3). The description adds a concrete worked example address, which slightly clarifies expected format beyond the schema's shorthand.

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 (Bitcoin mainnet address) and enumerates exactly what it returns: confirmed balance in sats and BTC, unconfirmed pending, total received/sent, and transaction counts. It also names the accepted address types (legacy, P2SH, bech32), which cleanly separates it from the sibling btc_fees tool.

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 concrete usage contexts — payment verification, confirming a deposit arrived, wallet monitoring — which tells an agent when this is the right call. It does not explicitly state when to use a sibling instead (e.g. btc_fees for fee estimation), so it stops short of full routing guidance.

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