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

Annotations cover the openWorld/write-shape profile, but the description adds genuinely non-structured behavior: a $0.003 USDC cost on Base, charged per successful call via x402. This is important operational context an agent must know before invoking. It does not explain why readOnlyHint is false, but the payment disclosure largely accounts for it.

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?

Three tight sentences: what it returns, when to use it, then the cost. Front-loaded with the resource and scope, and no filler.

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 compensates by enumerating the returned fields (sats and BTC balances, unconfirmed amount, received/sent totals, tx counts). Usage context and the pricing/payment mechanism are also present, leaving nothing critical missing for a one-param read.

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?

Single parameter with 100% schema description coverage, so baseline is 3. The description's mention of legacy/P2SH/bech32 roughly mirrors the schema's '1..., 3... or bc1...' format note and adds no syntax or edge-case detail beyond it.

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, unconfirmed pending, total received/sent, tx counts. The Bitcoin-specific framing cleanly separates it from the many sibling balance tools (eth_balance, base_balance, polygon_balance).

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 three concrete use cases: payment verification, deposit arrival checks, and wallet monitoring. It provides clear context for when to reach for this tool but names no explicit alternatives or exclusions among the dozens of sibling balance/chain tools.

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