Screwtape.ai

This connector has been deprecated

Duplicate listing. This connector has been replaced by ai.screwtape/screwtape.

Payment check

payment_check

Read-onlyIdempotent

Payment check: is this seller safe to pay, checked at the moment the agent pays. Compares the 402 price and payee with the seller's published listings when they can be fetched, screens the payee against a local denylist and the bundled OFAC SDN digital-currency address list, flags an over-price versus the intended amount, reuses the duplicate-payment check, and confirms the seller URL returns a valid 402. Returns allow, review or block with reasons and a signed receipt id. Fetches time out in about 2s and fail closed to review. $0.005 per call.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "payment_check"
  }
}

Input Schema

Name	Required	Description
`agent_id`	No	Optional agent or caller id, also used on the signed receipt.
`event_id`	No	Optional idempotency key for this check.
`seller_url`	No	The seller's paid HTTP URL.
`intended_amount`	No	USD the agent intends to pay.
`payment_required`	No	The seller's 402 PAYMENT-REQUIRED payload or base64 header value.

Output Schema

Name	Required	Description
`payee`	No
`checks`	No
`reasons`	No
`verdict`	No	allow, review, or block.
`amount_usd`	No
`receipt_id`	No
`request_id`	No
`verify_url`	No

Schema Changelog

Changes observed during successful MCP inspections.

AddedNov 10, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Beyond the annotations, the description discloses the concrete checks performed: 402 price/payee comparison, denylist and OFAC screening, over-price detection, duplicate-payment reuse, URL validation, and fail-closed behavior on timeout. It also states the output categories and the per-call cost, which are valuable behavioral details not covered by annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is front-loaded with the core question and then lists the checks efficiently. It is dense and mostly a single long sentence, but every part carries useful information and there is little wasted wording.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's complexity, the description covers what is checked, how failures are handled, what the return categories are, and the cost. With an output schema and rich annotations present, this is complete enough for an agent to invoke it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3. The description adds meaning by explaining how key inputs drive behavior: intended_amount is used for over-price flagging, seller_url must return a valid 402, and payment_required is compared against published listings.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource: it checks whether a seller is safe to pay at the moment of payment. It is clearly distinguishable from sibling tools like check_duplicate_invoice and try_check because it describes a pre-payment safety decision with allow/review/block outcomes.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The timing guidance is explicit: the check is performed at the moment the agent pays. It does not name alternatives or exclusion conditions, but the context is clear enough for an agent to know when to invoke it.

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

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