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

Annotations already declare destructive, non-idempotent, and open-world behavior, so the description's 'WRITE' and 'Not idempotent' are somewhat redundant. It does earn credit for spelling out the concrete consequence (two fulfillments on a double call), the customer email side effect, the required scope (write_fulfillments), and the endpoint.

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?

Four short sentences, front-loaded with 'WRITE', with no wasted words. The idempotency statement partially repeats the annotation, but it is short enough that it does not harm readability.

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 destructive, non-idempotent mutation with eight parameters and no output schema, the description covers safety signal, repeat-call risk, notification side effect, permission, and endpoint. It does not describe the returned fulfillment object or default status behavior, which are minor gaps for this schema.

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 the schema already documents every parameter, including the 'omit to fulfill the whole order' semantics for line_items. The description restates the partial-fulfillment idea and the notify_customer behavior without adding format or default detail 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?

States a specific verb and resource ('Mark an order ... as shipped') and scopes it to whole-order or partial line-item fulfillment. It is clearly distinguishable from listing tools like easystore_list_order_fulfillments, but it never names a sibling or an alternative explicitly.

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?

Implies when to use it (marking shipments) and gives an important caveat about repeat calls and the notify_customer side effect, but offers no explicit when-not guidance or comparison with alternatives such as easystore_cancel_order or easystore_list_order_fulfillments.

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