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

With no annotations, the description carries the full behavioral burden and discloses operator-only authorization, idempotency, and the exact return behavior when the invoice is already credited (success with credits_granted=0). It does not cover reversibility or detailed failure modes, but the key behavioral traits are present.

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 front-loaded with the core action, followed by restriction, use cases, and idempotency in a logical order. Every sentence contributes useful information without 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?

For a restricted mutation tool with no annotations, the description covers authorization, idempotency, and invocation contexts well. An output schema exists, so return values need not be explained. Some operational edge cases, such as invalid or unsettled invoices, remain unstated, but the definition is largely complete.

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 description coverage is 100%, so the schema already documents dpop_token, invoice_id, and patron_npub in detail. The description adds no parameter-level syntax, format, or constraints beyond what the schema provides, making 3 the appropriate baseline.

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 first sentence states a specific verb, target, and source: credit a patron's ledger from a BTCPay-settled invoice. The operator-only restriction distinguishes it from patron-facing credit tools such as purchase_credits and makes its purpose 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?

Explicitly states who may invoke it ('RESTRICTED to the operator') and what patrons should do instead (escalate to support). Concrete use cases such as check_payment races, ncred delivery hiccups, and Top-Off closures make the when-to-use condition clear.

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