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

No annotations are provided, so the description carries the full burden. It discloses critical behavioral traits: the out-of-band payment process (Stripe or USDC), the return of a live HTTP 402 challenge, and the cost ($2.00). It does not detail idempotency key behavior or error states, but the core mutation and payment flow are transparent.

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 sentences deliver complete intent, payment process, and cost. Every word is purposeful; the description is front-loaded with the primary action. No redundancy or filler.

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 simple tool with a single parameter and no output schema, the description covers return value (HTTP 402 challenge plus instructions) and key constraints (payment out-of-band). Missing details like idempotency retry behavior or error handling are minor gaps, but overall sufficient for an agent to invoke correctly.

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% with a clear description of the idempotency_key parameter. The description adds no additional meaning about this parameter beyond what the schema already provides. Baseline 3 is appropriate per guidelines.

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 'Request a new paid inbox' with a specific verb and resource. It distinguishes itself from sibling tools like delete_inbox and get_inbox by specifying the paid nature and unique return of a payment challenge, leaving no ambiguity about its function.

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 implies usage for creating a paid inbox and details the payment flow, but it does not explicitly state when to avoid this tool or recommend alternatives. Sibling tools exist (e.g., get_inbox for existing inboxes), but no direct comparison is provided, leaving the decision partially to inference.

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