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

Goes well beyond the annotations: explains the upsert semantics ('the newest call replaces the wallet on file'), the correction path for a bad address, and a privacy guarantee ('stores only a hash and a masked hint, never the raw address'). This adds real operational and security context that idempotentHint/destructiveHint alone do not convey.

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?

Front-loads the verb, resource, and endpoint in the first sentence, then adds three tight supporting sentences. There is slight echo between the description and the schema's target text about re-running and hash/masked-hint storage, but it stays compact and well-ordered.

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 4-param mutation tool with no output schema, the description covers the mutation semantics, idempotency, and privacy behavior that an agent needs. It does not describe the return payload, but with no output schema that is a minor gap and the safety profile is already carried by annotations.

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 rail const, target format (0x base address), kid, and token. The description adds essentially no parameter-level detail beyond what the schema states, so the baseline 3 applies.

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+resource (set/update the operator's x402 payout wallet) and pins the exact endpoint (PATCH /v1/agents/{kid}/payout). It also disambiguates scope by clarifying that Stripe payouts take a different path, so an agent won't confuse this with a general payout tool.

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?

Gives clear usage context — safe to re-run whenever, wrong addresses corrected by re-calling, and an explicit exclusion ('Stripe payouts go through the operator payout onboarding, not this tool'). It lacks a named alternative sibling tool, but none of the listed siblings handle payouts, so the routing guidance is effectively complete.

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