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

Annotations already declare readOnlyHint=true, and the description does not contradict that. The description adds valuable context beyond the annotation by disclosing data scale (200+ methods), the meaning of the Name field as a constant to consume, and filterability. This goes beyond the minimal read-only hint.

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 consists of three sentences that front-load the primary purpose, then provide usage examples and the calling pattern. Every sentence earns its place, and the '[DEMO]' marker is a minimal but relevant note. No redundancy or filler.

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?

Given the tool's simplicity (no required parameters, output schema present), the description is complete. It tells the caller how to invoke (no-args vs filter), what the output represents (constants for Method), and the scale (200+ methods). Nothing essential is missing for a read-only lookup of this type.

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%: Carrier has examples, PackageType has enum and explanation. The description does not add meaning beyond the schema; it only restates the Carrier filter option and mentions scale. This matches the baseline 3 for full schema coverage.

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 explicitly states the tool 'Returns supported shipping method constants, carrier, and package type,' which is a specific verb+resource that distinguishes it from sibling tools like get_rates (pricing) and get_order_ship_options (order-specific options). It further clarifies the purpose by explaining that the Name field is used in Packages[].Method for rate quotes and label purchase.

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 provides explicit usage instructions: 'Call with no parameters for all 200+ methods; filter by Carrier (USPS, FEDEX, UPS, etc.) for a shorter list.' It also ties the output to a concrete downstream use case. However, it does not explicitly name alternative tools or when-not-to-use scenarios, so it does not fully meet the 5-level criterion.

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