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

Beyond the annotations (which already declare read-only/idempotent/non-destructive), the description adds real behavioral detail: foreign and non-existent order numbers return the same 404 (anti-enumeration), and card token and BIN are withheld from output. This is substantive context an agent could not infer from structured fields.

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?

Purpose and return fields are front-loaded, followed by the safety/redaction notes, so the important content comes first. The trailing EN keyword list adds search noise but is a consistent convention; overall it is dense and mostly earns its length.

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?

With no output schema, the description compensates by listing the returned fields (order number, date, amount, credits, status, transaction, payment data) and noting the redactions. An agent has enough to invoke it and interpret the result correctly.

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% and the single order_id parameter is already documented in the schema, including its origin at the chargeup:sumup line of onto_credit_balance. The description largely restates this, 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?

States a specific verb and resource ('Beleg zu einer SumUp-Aufladung lesen') and enumerates the returned fields, so an agent knows exactly what the tool fetches. It is clearly distinguishable from sibling credit tools like onto_credit_balance and onto_credit_chargeup.

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?

Gives clear operating context: it is read-only, only returns the caller's own receipt, and explicitly points to onto_credit_balance as the source of the order number. It stops short of an explicit 'use this instead of X when Y' routing statement, but the prerequisite is well covered.

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