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

Annotations already supply readOnlyHint, idempotentHint, destructiveHint=false and closed-world hints, so the safety profile is covered. The description adds value beyond that: it is 'Free', and it discloses the availability states ('available or activation-ready', 'where active'), which tells the agent results may be conditional. It stops short of describing result shape or sorting, keeping it at a 4.

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, zero waste. The what is front-loaded, and the usage/alternative guidance follows immediately without repetition.

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?

With no output schema and no parameters, the description carries the burden of telling the agent what it gets back, and it does so at a conceptual level (list of payment rails with states). It does not specify result structure or ordering, but annotations and sibling context make this sufficient for correct invocation.

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?

Zero parameters, so there is nothing for the description to disambiguate; the baseline for a no-arg tool is 4. The text correctly implies no input is required.

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?

States a specific verb and resource ('read-only discovery of machine payment rails') and scopes it precisely to PaidHandshake, naming concrete rail types (Stripe-funded delegated wallets, x402 Base-USDC). It distinguishes itself from get_machine_wallet by contrasting discovery of options with inspection of one wallet.

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 it ('an autonomous buyer needs to choose how to pay') and names the alternative with its own selection condition (get_machine_wallet for inspecting an authenticated machine's balance and limits). Nothing is left to inference.

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