ebay_get_shipping_carriers

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

Annotations already declare readOnlyHint=true, so the safety profile is covered, and the description adds the useful detail that this is a Metadata API whose values are enums for shipment tracking plus a localization edge case (EBAY_CA without fr-CA returns English Canada). Still, most of that behavioral detail is a restatement of the acceptLanguage schema field, and nothing is said about auth requirements, caching, or rate limits.

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 core purpose is front-loaded in the first sentence and each sentence carries information, but the acceptLanguage sentence repeats what the schema already states, which is mild redundancy against a two-parameter 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 does explain the shape of the return ('Each shippingCarrier value is the enum to use when supplying shipment tracking') and ties it to a downstream tool, which is adequate for a two-param read. Minor gaps remain around authentication and how the localization value affects the result set.

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%, so both parameters are already documented in the schema, and the description's acceptLanguage sentence largely duplicates the schema text. The description adds no new syntax, defaults, or constraints beyond the schema, so the baseline 3 applies.

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 verb and resource ('list the shipping carriers supported on a marketplace') and pins the scope to a marketplace, so the agent knows exactly what is returned. It does not explicitly distinguish itself from the nearby 'get_shipping_services' sibling, which is the main reason this is a 4 rather than a 5.

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 downstream context ('Use the returned values when configuring fulfillment policies (ebay_create_fulfillment_policy)') and conditions for localization. However, it never states when to prefer this over alternatives or any prerequisites/exclusions, so it stops short of the explicit when/when-not guidance a 5 requires.

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