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

Goes beyond the annotations (which only declare readOnlyHint=false, openWorldHint=true) by disclosing the write effect: invoices are marked paid or partial, payment is allocated in order with the first paid in full. It also states the auth requirement and external-party impact. Still silent on edge cases like overpayment or duplicate submissions, so not a full 5.

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?

Front-loads the core purpose, then layers allocation rules before the policy notes. Mostly tight, though the confirmation/auth sentences could be trimmed without losing meaning.

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 mutation tool with no output schema, the description covers purpose, effect on invoices, allocation order, auth needs, and confirmation behavior. Sufficient for correct invocation, though the absence of an output schema leaves the returned result shape unstated.

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%, so the baseline is 3; the description exceeds it by explaining the allocation semantics of invoice_ids (first in full, next with the remainder) and the resulting paid/partial status, which the schema only hints at with 'paid in this order'.

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 ('Record a payment and attach it to one or more invoices') and elaborates the mechanism (payment linked to invoice_ids, applied in order). This is far more specific than a generic 'mark paid' sibling and lets an agent identify the operation without opening the schema.

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?

Provides prerequisites (Cotlet API key with app access) and a confirmation default that can be toggled, plus a warning to confirm because it 'reaches other people'. However, it never states when to choose this over close siblings like fakturownia_mark_invoice_paid, so the when-vs-alternative guidance is only implied.

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