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

Annotations already provide readOnlyHint=true and openWorldHint=true, so the safety profile is known. The description adds valuable behavioral context by specifying that both confirmed and unconfirmed balances are returned and that the unit is satoshis, which is beyond what annotations provide.

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?

The description is a single, dense sentence that immediately conveys the action, resource, network, and return unit. There is no fluff or redundant information; every word earns its place.

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?

For a simple one-parameter read-only tool with annotations and no output schema, the description is complete. It tells the agent what balance is returned (confirmed/unconfirmed), in what unit (satoshis), and on which network (mainnet). No additional context is necessary for correct invocation.

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?

The input schema already has a detailed description for the 'address' parameter, listing supported address types (P2PKH, P2SH, P2WPKH, P2WSH, P2TR), giving 100% schema coverage. The description only says 'for a Bitcoin address' and does not add further meaning, so the baseline of 3 is appropriate.

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?

The description clearly states a specific verb ('Get') and resource ('confirmed and unconfirmed balance for a Bitcoin address on Bitcoin mainnet'). It also distinguishes from the testnet sibling by explicitly saying 'mainnet', making the tool's scope unambiguous.

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?

The description provides clear context that this is for Bitcoin mainnet, which implicitly tells the agent to use the testnet sibling for testnet addresses. However, it does not explicitly name alternatives or exclusion criteria, so it falls short of a perfect 5.

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