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

With no annotations, the description carries the full burden and does disclose useful behavioral facts: the call is free ('Free — no credits required') and requires proof of npub ownership to prevent enumeration of balances. It does not state read-only or rate limits, but for a simple balance-check operation the main cost and auth behaviors are covered.

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 compact and front-loaded: the first sentence states the core action, the second paragraph clarifies scope and distinguishes the sibling, the third adds cost and security rationale. Every sentence earns its place with no redundancy.

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?

Given the output schema exists and the input schema is fully documented, the description covers the essential decision context: what balance is checked, when to use this vs the alternative, that it is free, and the auth requirement. The one completeness gap is the misnamed alternative tool, which slightly weakens the disambiguation in a large sibling list.

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 both parameters already have detailed descriptions in the schema. The description adds context about the meaning of the balance and the proof requirement, but does not add anything about npub or dpop_token beyond what the schema provides. This meets the baseline for fully-covered parameters.

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?

Description opens with a precise verb+resource: 'Check a patron's credit balance at this operator.' The second paragraph sharpens the scope by defining it as the patron's spending balance purchased via Lightning, and explicitly contrasts it with the operator's own Authority balance. This gives the agent a clear, unambiguous picture of what the tool does and how it differs from similar balance tools.

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 gives an explicit when-to-use signal: for the patron's spending balance. It also names an alternative: 'use authority_check_balance instead' for the operator's Authority balance. However, the alternative name is inaccurate — the actual sibling is taxsort_check_authority_balance — so the routing instruction is explicit but slightly imprecise.

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