Simulate a payment (test mode only)

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

Annotations only tell the agent this is a non-readonly, open-world, non-idempotent, non-destructive write; the description adds the substantive behavior: the invoice becomes paid and fulfilled, entitlements and license keys are issued, a receipt is generated, and webhook events fire. It also discloses the hard access constraint — test keys only, refused with a live key — which is nowhere in the annotations and materially changes whether the call is attempted.

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?

Purpose and test-mode restriction are front-loaded, and every sentence carries information. It is dense and somewhat run-on, packing defaults, side effects, and preconditions into long em-dash clauses that take a second read to parse.

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 mutation tool with no output schema and 60% param coverage, the description covers what's created, what the outcome modes do, how chain/asset resolve, and the auth constraint. The only unchecked box is the exact response payload, which retrieve_payment can supply.

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 60%, and the description compensates for the gaps: `chain` and `asset` have no schema descriptions at all, yet the description explains their default resolution and the refund-terms-accepted side effect. It also clarifies the mutual exclusivity of `id` and `payment_link` and the default of `outcome` to `full`, plus the underpaid/overpaid semantics the enum names do not convey.

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 definition names a specific verb and resource (simulate a payment) and immediately scopes it to test mode, which separates it from every live-money sibling in the list (create_refund, pay_links, create_checkout_session). The follow-on sentences spell out exactly what the outcome variants mean, so the agent knows what the tool will actually do before opening the schema.

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?

It gives concrete preconditions: `short` and `over` need the buyer's chain and asset chosen first, and `full` will auto-select the first stablecoin when no chain exists. It also explains the id-vs-payment_link entry path. It stops short of naming alternatives (e.g. when to use pay_links or create_checkout_session instead), so no exclusions are stated.

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