Simulate a customer bank transfer (test mode only)

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

Beyond the annotations, it discloses that the simulation flows through the live pipeline (payment reaches `succeeded`, webhooks fire) and enumerates concrete failure modes: 403 test_mode_only, 400 simulation_rejected for wrong amounts on exact-amount accounts, and 409 virtual_account_not_active. It also warns that a 202 only means acceptance and the outcome must be watched via the payment or events.

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 content is front-loaded with the test-mode constraint and the outcome semantics, and each sentence carries substantive information. The 'test mode only' constraint is repeated three times, which is redundant, though the emphasis is defensible for a high-risk-of-misuse tool.

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 simulation tool with no output schema, the description covers the safety constraint, the async nature of the 202 response, how to observe the outcome, and the specific error conditions an agent may hit. Nothing material needed to call it correctly is missing.

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 description coverage is 100%, so the schema already documents all four parameters including the refund behavior of sender_account_number. The description adds only indirect parameter meaning (amount correctness against exact-amount accounts), which is the baseline expectation when the schema does the heavy lifting.

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 states a specific verb and resource ('Simulate a customer bank transfer') and immediately scopes it to test virtual accounts, which cleanly separates it from the live-money sibling create_transfer. An agent can identify what this does without 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 a clear usage context: test mode only, requires an sk_test_ key, and the transfer must target one of your test virtual accounts. It does not explicitly name create_transfer as the live-mode alternative, so the when-not-to-use routing is implied rather than stated.

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