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

Annotations are empty, so the description carries the full burden. It does disclose real behavior: a confirmation gate before execution and a hard PIN requirement for completion, plus api_key/token auth. It omits irreversibility, failure behavior, and rate limits, which matters for a money-moving mutation.

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 core sentence 'Charges the account based on a presented QR-code or NFC card' is repeated verbatim in the opening and again in the body, wasting space. The rest is a functional JSDoc block, and key constraints (confirmation, PIN) are front-loaded, but the duplication costs it.

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 7-parameter payment mutation with no annotations and no output schema, the definition covers inputs well but returns only 'a json object' and says nothing about error cases, idempotency, or what a successful charge response contains. Adequate but leaves meaningful gaps for a high-stakes tool.

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 0%, so the description must compensate, and it largely does: it disambiguates account_fk (an int database ID, not an address, may not be 0, and is the merchant receiving payment) from account_address (the account charged), and clarifies token provenance (/access/login) and that pin belongs to account_address. Only amount and note get no added meaning.

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 ('Charges the account') plus the triggering mechanism ('presented QR-code or NFC card'), which distinguishes it from generic siblings like account_pay or account_send. However it never names or excludes those siblings explicitly, so the differentiation is inferred rather than stated.

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?

It gives an operational instruction ('Confirm (yes/no) before executing') and a prerequisite ('The payer must present a valid PIN'), which implies the usage context. But with many overlapping payment siblings (account_pay, account_send, account_wire, account_merchant_voucher_redeem), there is no explicit when-to-use-this-vs-alternatives guidance.

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