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

The clause 'fields you leave out keep their values' is genuine behavioral context beyond the annotations — it tells the agent this is a PATCH-style edit, not a full replace. However, annotations declare destructiveHint=true and idempotentHint=false, and the description never explains what is destructive, whether in-flight labels are affected, or how non-idempotency arises.

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?

A single tight sentence with the operation front-loaded and the amendment rule second. Nothing is wasted, though the extreme brevity means several needed disclosures were dropped rather than compressed.

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 14-parameter destructive mutation with no output schema, the description is thin: it does not cover permissions, what changes mean for existing shipments/labels, or what 'destructive' entails. Only the partial-update rule is provided.

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 43%, so the description must compensate. It does convey the most important parameter rule — 13 of 14 params are optional and omission preserves existing values — but says nothing about the dimension params, the packaging/signature/return_label enums, or how irregular interacts with length/width/height.

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 ('Changes') and resource ('a Saved Package'), and the partial-update clause implicitly separates it from create_saved_package and delete_saved_package. It never names those siblings, so differentiation is inferable rather than explicit.

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?

No when-to-use, when-not-to-use, or prerequisite guidance beyond the schema's note that package_id comes from list_saved_packages. The partial-update framing implies the right context (editing an existing package) but the description does not route the agent to alternatives or warn about preconditions.

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