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

Adds substantial value beyond the annotations: it discloses that an email is actually sent, that the form URL is deliberately withheld from chat, that the destination is read inside the form (image never uploaded), and that returns are masked. It doesn't explain the destructiveHint=true surface (e.g., whether calling again overwrites or resends) or any rate limits, which keeps it below top marks.

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 destination options are front-loaded, and the rest is procedural safety guidance that earns its place. It is dense and runs long, but no sentence is filler; a light trim of the parenthetical detail would tighten it.

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, the description compensates by describing the return values (masked destination on file and masked address the link went to) and by explaining the security model and what the agent must tell the user. An agent can invoke and follow up correctly without further information.

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 single parameter customerKey is fully documented in the schema (100% coverage), including the personal-token-URL omission case. The description adds nothing about the parameter, so the schema carries all the weight, matching the baseline for high coverage.

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 concrete verb and resource (email the referrer a link to the payout-registration form) and enumerates the two destinations it covers (Thai PromptPay QR, stablecoin USDC on Base / USDM on Cardano). This is clearly distinct from siblings like register_customer or my_referrals, which deal with identity and referral listing rather than payout destination.

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 an explicit trigger: 'Call this when the user wants to register, see, or change their payout destination,' covering read and write intents. It does not name any sibling alternative or exclusion, but no sibling appears to overlap this domain.

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