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

Provides extensive behavioral disclosure beyond annotations: the key is ephemeral (memory-only, never persisted/logged/returned), expires on idle or afg_discard_wallet, and requires a mock ledger. This adds significant context that annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=true) do not convey, and it does not contradict them.

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?

Every sentence in the description earns its place. It front-loads the core purpose, then efficiently covers key handling, expiration, return value, usage condition, and alternative. No fluff or repetition; the structure is logical and scannable.

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 no-parameter tool with no output schema, the description fully compensates: it explains what is returned, when it is refused, how the key is handled, and the test-only nature. An agent has all necessary information to decide whether to invoke it and what to expect.

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 tool has zero parameters, so the schema provides no details. The baseline for 0 params is 4; the description cannot add parameter-specific meaning because none exist. The description does clarify the return value (wallet_handle and address), but that is not parameter semantics.

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?

Clearly states the specific verb 'Create' and the resource 'throwaway sandbox wallet' for the client. It also distinguishes itself from the sibling tool afg_prepare_signed_request by mentioning that as an alternative, so an agent can immediately tell when to use this tool versus that one.

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?

Explicitly states when to use (for a test-money mock ledger) and when not to (prefer afg_prepare_signed_request if you already have a wallet). Also warns 'TEST MONEY ONLY' and notes the refusal condition, giving clear contextual boundaries.

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