CrossingKey MCP

Purchase OpenAPI Quality Audit

openapi.quality_audit

Idempotent

PAID $1.00 USDC on Base via x402. Evaluates structural quality and required fields in an OpenAPI document. Calling this MCP tool does not spend funds; it returns the exact PAYMENT-REQUIRED challenge and canonical paid execution endpoint.

Input Schema

Name	Required	Description	Default
`spec`	Yes	Parsed OpenAPI document to audit.

Output Schema

Name	Required	Description	Default
`asset`	No
`error`	No
`input`	No
`price`	No
`pay_to`	No
`status`	No
`accepts`	No
`network`	No
`resource`	No
`capability`	No
`extensions`	No
`purchaseId`	No
`instruction`	No
`x402Version`	No
`entitlementId`	No
`execution_url`	No
`execution_mode`	No
`payment_required`	No
`payment_required_header`	No
`settlement_expectations`	No
`confirmation_expectations`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed10 schema fields changedOct 15, 2026

changedOutput schema / additionalProperties
```
Previous value: -falseNew value: +true
```

addedOutput schema / properties / accepts

Added value: +{
+  "items": {
+    "additionalProperties": true,
+    "properties": {},
+    "type": "object"
+  },
+  "type": "array"
+}

addedOutput schema / properties / entitlementId
```
Added value: +{
+  "type": "string"
+}
```
addedOutput schema / properties / error
```
Added value: +{
+  "type": "string"
+}
```

addedOutput schema / properties / extensions

Added value: +{
+  "additionalProperties": true,
+  "properties": {},
+  "type": "object"
+}

addedOutput schema / properties / purchaseId
```
Added value: +{
+  "type": "string"
+}
```

addedOutput schema / properties / resource

Added value: +{
+  "additionalProperties": true,
+  "properties": {},
+  "type": "object"
+}

addedOutput schema / properties / status
```
Added value: +{
+  "type": "string"
+}
```

addedOutput schema / properties / x402Version

Added value: +{
+  "const": 2,
+  "type": "number"
+}

removedOutput schema / required

Removed value: -[
-  "payment_required",
-  "execution_mode",
-  "capability",
-  "input",
-  "price",
-  "asset",
-  "network",
-  "pay_to",
-  "execution_url",
-  "payment_required_header",
-  "settlement_expectations",
-  "confirmation_expectations",
-  "instruction"
-]

Changed1 schema field changedOct 2, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "asset": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "capability": {
+      "type": "string"
+    },
+    "confirmation_expectations": {
+      "type": "string"
+    },
+    "execution_mode": {
+      "type": "string"
+    },
+    "execution_url": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "input": {
+      "additionalProperties": true,
+      "properties": {},
+      "type": "object"
+    },
+    "instruction": {
+      "type": "string"
+    },
+    "network": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "pay_to": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "payment_required": {
+      "const": true,
+      "type": "boolean"
+    },
+    "payment_required_header": {
+      "type": "string"
+    },
+    "price": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "settlement_expectations": {
+      "type": "string"
+    }
+  },
+  "required": [
+    "payment_required",
+    "execution_mode",
+    "capability",
+    "input",
+    "price",
+    "asset",
+    "network",
+    "pay_to",
+    "execution_url",
+    "payment_required_header",
+    "settlement_expectations",
+    "confirmation_expectations",
+    "instruction"
+  ],
+  "type": "object"
+}

AddedSep 22, 2026

TDQS

A3.9/5.0

Behavior5/5

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

Goes well beyond the annotations by disclosing the cost ($1.00 USDC on Base via x402), the crucial non-obvious fact that calling it does not spend funds, and that it returns a PAYMENT-REQUIRED challenge plus the canonical paid execution endpoint. This reconciles the otherwise surprising readOnlyHint=false and fully explains the two-phase paid flow.

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?

Three tight sentences with the price and payment model front-loaded, then purpose, then the non-spending clarification. Every sentence earns its place, though the leading price line is slightly jarring as an opener.

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

Completeness4/5

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 need no description, and the single param is fully documented. The description covers cost, funds behavior, and the payment challenge, but does not address how the agent fulfills payment (e.g., wallet/auth prerequisites) or differentiate among the x402 sibling audits.

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?

There is a single parameter ('spec') with 100% schema description coverage, so the schema already documents it as a parsed OpenAPI document. The description adds no format or syntax 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.

Purpose4/5

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

States a specific verb and resource: 'Evaluates structural quality and required fields in an OpenAPI document.' The agent can tell this audits an OpenAPI spec. However, it never distinguishes itself from closely named siblings like x402.compatibility_audit, x402.purchase_path_audit, or mcp.schema_audit, so sibling differentiation is left to inference.

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

Usage Guidelines3/5

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

Usage is implied by the resource (audit an OpenAPI doc), and the description usefully notes that calling it does not spend funds and returns the payment challenge. But it gives no explicit when-to-use vs when-not guidance, nor does it point to an alternative audit tool when a different check is wanted.

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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