set_webhookPATCH /auth/v1/agent/webhook. Sets https callback_url (required before hmac/rotate), optional X25519 jwe_public_key for card_encrypted, optional email for 3DS OTP. Not SMS. HMAC plaintext is shown once when a URL is first accepted.
| Name | Required | Description | Default |
|---|---|---|---|
| No | |||
| callback_url | No | ||
| jwe_public_key | No |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond the annotations (readOnly=false, idempotent=true, destructive=false), the description discloses a crucial one-time behavior: 'HMAC plaintext is shown once when a URL is first accepted.' It also reveals the stateful prerequisite with hmac/rotate. This adds real operational value that an agent cannot infer from annotations or schema alone.
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 description is compact and front-loaded: endpoint, primary action, optional parameters, then the critical one-time HMAC caveat. Every sentence adds information, and the 'Not SMS' exclusion is a useful terse clarification rather than fluff.
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 simple three-parameter configuration tool, the description covers all parameters, key prerequisites, and the most important behavioral caveat. It does not describe the response shape or error conditions, and with no output schema those are minor omissions for invoking the tool correctly.
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?
With schema description coverage at 0%, the description carries the full semantic burden and does so well: callback_url is tied to hmac/rotate, jwe_public_key is tied to card_encrypted, and email is tied to 3DS OTP. It does not provide exhaustive format details or explicitly note that all parameters are optional, but it gives enough meaning beyond the raw schema.
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 operation ('Sets https callback_url'), lists the optional parameters and their purposes, and even notes the callback_url prerequisite for hmac/rotate. This is enough for an agent to distinguish it from related sibling tools like rotate_hmac without opening their schemas.
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?
The description provides clear usage context: callback_url must be set before hmac/rotate, jwe_public_key is for card_encrypted, and email is for 3DS OTP. It also adds an explicit exclusion ('Not SMS'). However, it does not name alternative sibling tools or say when NOT to use this tool beyond the SMS note.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Most tools target distinct resource-action pairs: card creation, card detail, top-up, eSIM/gift purchase, KYT initiation, KYT polling, and history are all separated. The KYT family is the main risk area, but the descriptions clearly distinguish check, get, checks, and quote.
The dominant pattern is verb_noun snake_case, e.g., list_cards, purchase_gift, topup_card, get_balance. The KYT group is inconsistent—kyt_check, kyt_check_get, kyt_checks, kyt_quote—and set_webhook/rotate_hmac break the pattern slightly, but the overall set remains predictable.
19 tools is above the typical 3-15 sweet spot, but the count is justified by the range of spend rails and supporting operations: cards, eSIM, gift cards, KYT screening, notifications, and webhook management. No tool feels truly redundant, though the KYT cluster adds some bulk.
Core purchase and card workflows are covered: create, topup, details, list, and buy operations exist for cards/eSIM/gifts, plus deposit and KYT screening. However, there is no transaction/spend history, no card freeze or block action, and no explicit purchase status/refund flow, which are notable gaps for a spend-focused server.