geld machen x402 agent utilities

Phantom Seller Scan: Is payTo Economically Dead?

phantom-seller-scan

Read-onlyIdempotent

Check whether an x402 URL's payTo actually receives Base USDC (economically live vs phantom). Use when before integrating or paying an unknown x402 endpoint. Not for listing many sellers (use phantom-allowlist). Returns a free sample plus the paid URL and pay steps (no charge here); the full result costs $0.03 Base USDC via x402.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`query`	No	Input for the paid endpoint: https x402 endpoint URL.

Output Schema

TableJSON Schema

Name	Required	Description
`sku`	Yes
`note`	No
`payTo`	No
`price`	No
`method`	No
`network`	No
`paid_url`	Yes
`how_to_pay`	Yes
`teaser_url`	No
`your_input`	No
`free_teaser`	No	Free sample output of this SKU (truncated); null if unavailable.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 6, 2026

addedOutput schema / properties / free_teaser

Added value: +{
+  "description": "Free sample output of this SKU (truncated); null if unavailable."
+}

Changed1 schema field changedOct 6, 2026

changedInput schema / properties / query / description

Previous value: -"Optional input (e.g. url / address / text) to pass to the paid endpoint as ?q= or JSON body."New value: +"Input for the paid endpoint: https x402 endpoint URL."

Changed1 schema field changedOct 6, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "how_to_pay": {
+      "type": "string"
+    },
+    "method": {
+      "type": "string"
+    },
+    "network": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "note": {
+      "type": "string"
+    },
+    "paid_url": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "payTo": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "price": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "sku": {
+      "type": "string"
+    },
+    "teaser_url": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "your_input": {}
+  },
+  "required": [
+    "sku",
+    "paid_url",
+    "how_to_pay"
+  ],
+  "type": "object"
+}

First observedOct 6, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely new context: a free sample is returned with the paid URL and pay steps at no charge, while the full result costs $0.03 Base USDC via x402. That pricing/payment boundary is exactly what annotations cannot express. It stops short of describing rate limits or auth requirements.

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

Conciseness5/5

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

Three tight sentences: what it does, when to use it vs the alternative, and what it returns/costs. No filler, and the core purpose is front-loaded ahead of usage and pricing detail.

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?

An output schema exists, so return values needn't be spelled out, yet the description still flags that a free sample precedes the paid result. Combined with the explicit alternative routing and cost disclosure, an agent has everything needed to call this correctly.

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 description coverage is 100% and the single 'query' parameter is fully documented in the schema as the https x402 endpoint URL. The description restates that it takes an x402 URL but adds no format, validation, or example detail beyond the schema, so the baseline 3 applies.

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?

States a specific verb (check) and a precisely-scoped resource: whether an x402 URL's payTo actually receives Base USDC (economically live vs phantom). It also names the sibling it is not (phantom-allowlist), so an agent can route without opening either schema.

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

Usage Guidelines5/5

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

Gives an explicit trigger ('Use when before integrating or paying an unknown x402 endpoint') and an explicit exclusion with the alternative named ('Not for listing many sellers (use phantom-allowlist)'). Both when-to-use and when-not are covered.

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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