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

The description adds valuable behavioral context beyond annotations: it reveals that the tool returns a Stripe checkout URL rather than completing the order, and explains session key handling (requires one from a prior call or auto-creates). Annotations already indicate mutations but not this specific flow.

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 is extremely concise with two sentences, each carrying essential information: the core action and the key behavioral details (return value and session key handling). No wasted words.

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 moderate complexity (3 parameters, no output schema, no nested objects), the description covers all critical aspects: what it does, what it returns, and the session key dependency. It provides enough context for an AI agent to use the tool correctly without additional explanation.

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?

The input schema already provides full descriptions for all three parameters (100% coverage). The description reiterates the session key behavior but does not add new semantic meaning beyond what the schema provides. Baseline score of 3 is appropriate.

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 clearly states the verb 'Create' and the resource 'order for an eSIM package'. It distinguishes from siblings like 'buy_topup' by specifying it returns a Stripe checkout URL for payment, and from 'check_order_status' by focusing on order creation.

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?

The description provides clear contextual guidance by stating it requires a session key or creates one automatically, indicating it follows a previous tool call. However, it does not explicitly exclude alternatives like 'buy_topup' or state when to prefer this tool over others, so it slightly lacks exclusionary guidance.

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