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

Beyond the annotations, the description reveals that the tool appends a line, that the values are user-stated rather than sourced from other stores, and that the action affects shortfall calculations. It could say more about duplicate calls or matching behavior, but it adds meaningful behavioral context without contradicting annotations.

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 two focused sentences with the action front-loaded and the most important qualification immediately after. Every sentence earns its place, and there is no filler or redundant restating of the schema.

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 simple mutation tool with complete schema documentation and no output schema, the description supplies the essential operational context: it adds to a packing list, affects shortfall, and does not read from other stores. It does not explain duplicate handling or failure modes, but those are minor given the tool's low complexity.

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?

The input schema already documents all four parameters with 100% coverage, so the baseline is 3. The description names three of the four parameters but adds no extra format, constraints, or semantic detail beyond what the schema provides.

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 states a specific action ('Add an ordered line to a packing list') and names the payload fields (SKU, description, quantity). It is clear about the resource and purpose, but it does not explicitly differentiate from sibling tools such as pack_item or packing_shortfall.

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 clear context: use this to declare what the order says so the shortfall becomes real, and it explicitly notes that no data is read from quotes, work orders, or invoices. It lacks an explicit 'when not to use' or a named alternative, so it stops short of full guidance.

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