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

No annotations provided, so description carries full burden. It discloses that the operation is free (no credits required) and requires proof of npub ownership to prevent enumeration. Does not describe error handling or rate limits, but for a simple read operation this is adequate.

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 concise sentences: states purpose, distinguishes alternative, and notes key requirements. No filler; every sentence adds value. Front-loaded with primary purpose.

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?

Output schema exists, so return values are covered. Description covers purpose, auth requirement, cost, and alternative. For a balance-checking tool, this is comprehensive and leaves no obvious gaps.

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%, but description adds significant value beyond schema: explains dpop_token format in detail (raw JSON, not base64, specific kind, tag requirements, expiration, nonce recommendation). This clarifies usage beyond the schema's description.

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 explicitly states the tool checks a patron's credit balance, with specific verb ('check') and resource ('balance'). It distinguishes from sibling 'authority_check_balance' by clarifying scope (patron vs operator balance). No ambiguity.

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?

Explicitly states when to use (check patron spending balance) and when not to (for operator's own balance, use authority_check_balance). Also highlights that it's free and requires proof of npub ownership, setting context for usage constraints.

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