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

Annotations already declare a non-read-only, non-destructive, non-idempotent, closed-world operation. The description adds domain rules such as line kinds and positive credit amounts, plus 'Checked at once,' but that phrase is ambiguous and does not explain atomicity, duplicate rejection, or permission requirements.

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 compact and front-loads the invoice line format with no redundant sentences. 'Checked at once' is terse to the point of ambiguity, slightly reducing clarity.

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 three-parameter mutation with an output schema and safety annotations, it covers the most complex parameter and a key domain rule. It still leaves tool/period semantics, duplicate behavior, and sibling choice unexplained, so it is only adequately 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?

With 0% schema description coverage, the description carries the full burden. It richly defines the lines array item fields, including kind values and quantity meaning, but does not explain the tool parameter's maxLength or the period format beyond 'for a month'.

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 description identifies the resource (a coding tool's invoice for a month) and the line-item structure, but it is a noun phrase rather than an explicit verb and does not distinguish this tool from siblings like add_bill or add_credits. The title supplies 'Add', so creation can be inferred, but the description alone is only moderately clear.

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?

There is no guidance on when to use this tool versus add_bill, add_credits, or import_csv. It also does not state prerequisites, duplicate handling, or whether it is specifically for coding tools.

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