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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered. The description adds the mode-mutual-exclusivity constraint, but says nothing about return shape (list vs. single object), pagination, or behavior when an id is not found — gaps that matter for a lookup tool.

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?

Two short sentences, with the resource scope front-loaded before the constraint. The trailing 'GetCustomerShipTo' token is unexplained and slightly wasteful, keeping it from a 5.

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 two-parameter, read-only lookup with no output schema and full schema coverage, the description covers the resource, both modes, and their mutual exclusivity. Only the return shape and not-found behavior are left implicit, which is a minor gap at this 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?

Schema coverage is 100%, so both parameters are already documented, which sets a baseline of 3. The description earns an extra point by supplying the 'exactly one' constraint that the schema alone does not express (required is empty), preventing an agent from passing both or none.

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 the resource (saved ship-to/stop addresses of a customer) and the two retrieval modes (all by customer id, or one by ship-to id), which distinguishes it from siblings like ecourier_get_customer. It reads as a noun phrase rather than a verb, relying on the name/title for the 'list' action, so it falls just short of the top score.

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?

'Give exactly one' is an explicit invocation constraint that tells the agent to choose between the two modes rather than combining them. There are no named alternatives or when-not conditions, but the mode-selection guidance is unambiguous.

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