SpendPreflight

Historical x402 Quote Check

quote_check

Read-only

Use when you need an exact quote compared with cached public price and recipient evidence. Compare a supplied x402 quote with the latest comparable cached public unpaid quote and disclosed retained history. Scout keeps only the latest probe; the separate public index can retain seven days. $0.001 USDC on Base for a usable comparison, no trial. Missing/stale/ambiguous evidence returns unknown without charge. Never fetches or pays the target. Informational historical comparison, not payment approval or loss prevention. Price: 0.001 USDC. Minimal input example: {"url":"https://api.example.com/data","amount":"10000","payTo":"0x1111111111111111111111111111111111111111","asset":"0x833589fcd6edb6e08f4c7c32d4f71b54bda02913","network":"eip155:8453"}. Illustrative output excerpt: {"status":"unknown","baseline":null,"multiple":null,"suggested_max_amount_per_payment":null,"not_charged":true}. Illustrative output excerpt, not a live result, signature, approval or guarantee. Freshness/data/availability checks still apply. How to pay (MCP): Unknown evidence returns without charge; a usable comparison requires payment. No shared trial. Use an x402-capable MCP client. A generic MCP connector without payment support cannot complete a paid continuation. On payment required, STOP. Inspect the exact accepts amount, asset, network and payTo; obtain explicit wallet/budget approval before continuing. Only after approval, let the configured x402 MCP client attach its signed payload in _meta["x402/payment"] and retry the same tools/call arguments. Never send a separate USDC transfer or paste keys into tool arguments. Never silently fall back from free access to payment. If a signed attempt has an unknown outcome, inspect that authorization/transaction; do not create another automatically.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "url": "<url>",
      "amount": "<amount>",
      "payTo": "<payTo>",
      "asset": "<asset>",
      "network": "<network>"
    },
    "name": "quote_check"
  }
}

Input Schema

Name	Required	Description
`url`	Yes	Required. Exact public resource URL string, including path; no credentials. Use the current published example in OpenAPI when available.
`asset`	Yes	Required. Quoted token asset identifier string; EVM assets use a 0x-prefixed 20-byte contract address. Example: 0x833589fcd6edb6e08f4c7c32d4f71b54bda02913 (native Base USDC).
`payTo`	Yes	Required. Quoted recipient identifier string; EVM recipients use a 0x-prefixed 20-byte address. Example: 0xBf4164e07552e4c1b1B1597E72C7acAA3F0a1c58.
`amount`	Yes	Required. Quoted amount as a nonnegative atomic-unit integer string, not decimal USDC. Example: "10000" = 0.01 USDC at six decimals.
`method`	No	Optional. Advertised HTTP method string, not a new target request. Example: GET. Supply when cached methods are ambiguous.
`network`	Yes	Required. Payment network identifier string; use the quoted CAIP-2 identifier. Example: eip155:8453.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedNov 9, 2026

changedInput schema / properties / url / description

Previous value: -"Required. Exact public resource URL string, including path; no credentials. Example: https://1gateway.dev/v1/calendar/holidays."New value: +"Required. Exact public resource URL string, including path; no credentials. Use the current published example in OpenAPI when available."

Changed1 schema field changedNov 7, 2026

changedInput schema / properties / url / description

Previous value: -"Required. Exact public resource URL string, including path; no credentials. Example: https://api.example.com/data."New value: +"Required. Exact public resource URL string, including path; no credentials. Example: https://1gateway.dev/v1/calendar/holidays."

Changed6 schema fields changedNov 4, 2026

addedInput schema / properties / amount / description

Added value: +"Required. Quoted amount as a nonnegative atomic-unit integer string, not decimal USDC. Example: \"10000\" = 0.01 USDC at six decimals."

addedInput schema / properties / asset / description

Added value: +"Required. Quoted token asset identifier string; EVM assets use a 0x-prefixed 20-byte contract address. Example: 0x833589fcd6edb6e08f4c7c32d4f71b54bda02913 (native Base USDC)."

addedInput schema / properties / method / description

Added value: +"Optional. Advertised HTTP method string, not a new target request. Example: GET. Supply when cached methods are ambiguous."

addedInput schema / properties / network / description

Added value: +"Required. Payment network identifier string; use the quoted CAIP-2 identifier. Example: eip155:8453."

addedInput schema / properties / payTo / description

Added value: +"Required. Quoted recipient identifier string; EVM recipients use a 0x-prefixed 20-byte address. Example: 0xBf4164e07552e4c1b1B1597E72C7acAA3F0a1c58."

addedInput schema / properties / url / description

Added value: +"Required. Exact public resource URL string, including path; no credentials. Example: https://api.example.com/data."

AddedOct 27, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Rich disclosure beyond the annotations: cost of $0.001 USDC on Base, no-charge behavior for missing/stale/ambiguous evidence, the Scout latest-probe-only vs seven-day public index retention distinction, and a full x402 payment/STOP/retry protocol with explicit prohibition on separate USDC transfers or silent fallback. The only tension is that readOnlyHint=true and destructiveHint=false sit awkwardly with a tool that moves funds out of the caller's wallet, but the description itself is candid about the charge, so an agent is not misled.

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

Conciseness3/5

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

Front-loading is good — the use condition and scope come first — but the text is bloated: the price is stated twice ('$0.001 USDC on Base' and 'Price: 0.001 USDC'), the 'Illustrative output excerpt' label appears twice for a single excerpt, and the input example repeats the schema's own example. The payment-safety content earns its place; the duplication does not.

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?

With no output schema, the description compensates by sketching the return shape (status, baseline, multiple, suggested_max_amount_per_payment, not_charged) and clearly labelling it illustrative. Cost, charge/no-charge conditions, data retention windows, failure modes and the paid-retry mechanics are all covered, which is more than enough for a read-only comparison tool with six parameters.

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

Parameters3/5

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

Schema coverage is 100% and each field already documents format, examples and constraints, so the baseline of 3 applies. The description's minimal input example and the note that 'method' helps when cached methods are ambiguous duplicate what the schema descriptions already say rather than adding new semantic meaning.

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

Purpose4/5

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

States a specific verb and resource: compare a supplied x402 quote against the latest comparable cached public unpaid quote plus retained history. It also draws a boundary ('informational historical comparison, not payment approval or loss prevention') that implicitly separates it from payment-approval siblings such as preflight_payment, though it never names an alternative outright.

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 opening 'Use when you need an exact quote compared with cached public price and recipient evidence' gives a clear triggering condition, and the negatives ('never fetches or pays the target', 'not payment approval or loss prevention') define what it is not for. It stops short of the 5 bar because no sibling tool is named as the alternative for the excluded payment-approval use case.

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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