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

Annotations already declare readOnly; the description adds real value beyond them — OAuth requirement, no provider call for balance_amount, and what type=esim rows include (iccid, install_url, qr_code_url). Doesn't cover rate limits or pagination, so not a 5.

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?

Front-loaded with the core action and auth constraint; sentences are dense but mostly earn their place. The final 'decode nested consumption' sentence is somewhat cryptic.

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?

An output schema exists so return values needn't be explained, yet two of three parameters (limit, delivery_status) remain undocumented in both schema and description. Adequate for the main use case but with clear gaps.

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 0%, so the description carries the burden. It explains type=esim enrichment and the balance_amount/list semantics, but leaves the topup/giftcard enum values, limit, and delivery_status undocumented. Partial compensation.

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 — list completed or refunded orders for the authenticated user — and the OAuth/guest-checkout constraint implicitly distinguishes it from guest_order_lookup and get_order_status. Clear, though it doesn't name siblings 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?

Specifies the condition (authenticated user, no guest checkout), which routes guest flows to guest_order_lookup. Lacks explicit exclusion wording or direct sibling naming, but context is clear.

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