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

Annotations only flag a non-read-only, open-world, non-destructive mutation, but the description adds real context: it changes the books and invoice status, partial payments leave the invoice open, confirmation is on by default but can be switched off, the user must be consulted because it reaches other people, and a Cotlet API key with app access is required. This is meaningfully more than the annotations provide.

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 purpose in the opening sentence and keeps each clause purposeful (partial payment, side effects, confirmation, auth). The trailing confirmation/API-key sentences are slightly boilerplate but still operationally relevant, so only minor trimming is warranted.

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 four-required-param mutation with no output schema, the description covers side effects, partial-payment behavior, confirmation gating and auth requirements. Return value details are not needed since no output schema exists; only explicit sibling routing is missing.

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 date, amount, account and invoice_id with formats and examples. The description paraphrases date/amount/account but adds no syntax or constraint beyond the schema, so the baseline 3 applies.

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 (register/book a customer payment) and resource (an invoice), and adds the financial effect (clears the receivable). It is clearly distinct from create/publish/send siblings, but it never names an alternative sibling explicitly, so it stops short of full differentiation.

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?

Explains a useful usage nuance (an amount below the total leaves the invoice open as a partial payment), which implies when the tool is appropriate. It does not, however, say when to prefer it over alternatives such as creating a journal entry or sending an invoice, leaving routing to inference.

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