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

Annotations already cover the readOnly/openWorld safety profile, and the description adds high-value context beyond them: the $0.003 USDC cost, the x402 payment rails (Base, Solana, Polygon, Arbitrum), that compliant clients pay automatically, and a free-sample path. Cost and payment behavior are exactly the operational traits an agent needs and are not derivable from annotations or schema.

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 and output fields, then support scope, then pricing, then example. Slightly dense and the pricing sentence could be trimmed, but every sentence carries operational information rather than 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 does the full job: it enumerates return fields (balances, totals, tx count, recent transactions with net amount, confirmations, fee), address compatibility, cost, and a callable example. An agent has everything needed to decide and invoke 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%, so the baseline is 3, and the description earns above that by clarifying what 'Bitcoin address' actually accepts (bc1 SegWit/Taproot, 1, and 3 on mainnet) and demonstrating the params via a worked example with a concrete address and limit=3.

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+resource ('Bitcoin address lookup for agents') and immediately enumerates the returned data (confirmed/pending balance in BTC and USD, total received/sent, tx count, latest transactions). The scope ('Bitcoin mainnet', bc1/1/3 address types) distinguishes it from siblings like btc_tx, evm_balance, or tron_address without the agent 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 concrete when-to-use cases ('check a payment, a treasury or a counterparty wallet'), which is more than most siblings offer. However, it never names an alternative (e.g., btc_tx for a single transaction or wallet_portfolio for multi-chain) or states when not to use it, so routing still requires inference.

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