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

Annotations only carry negative hints (not read-only, not idempotent, not destructive), so the description must bear the burden of behavior. It discloses a meaningful behavioral constraint: only 3 lists can be open at once on the free tier, and shipping or cancelling frees a slot. This goes beyond the annotations and helps the agent anticipate quota-related failures.

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 sentences with no filler. The core action and return value are front-loaded, and the quota behavior earns its place as operational guidance an agent needs before calling the tool.

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 usefully states what is returned: the PL number plus order reference, consignee, ship-to, and date. It also covers the free-tier limitation. It is not exhaustive about error conditions or edge cases, but it is complete enough given the rich schema and the quota disclosure.

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 86%, so the parameters are already well documented in the schema. The description adds little beyond echoing reference, consignee, ship-to, and date; it does not explain note, duplicate_ok, or reference_kind beyond what the schema already provides. Baseline 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?

The description names a specific action ('Open a packing list against an order') and a concrete resource, and states the returned artifact ('PL-YYYY-NNNN number'). It is clearly differentiated from sibling tools like packing_list_list, packing_list_show, and packing_list_delete, which describe listing, viewing, and deleting rather than opening.

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?

The description implies the tool is used when opening a packing list against an order, and the free-tier quota adds operational context. However, it does not explicitly state when to prefer this over alternatives such as packing_slip, pack_item, or packing_list_show, nor does it give exclusions or when-not-to-use guidance.

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