EdgeScreen x402 Security Screening

by dev.workers.asostudio.aso-x402-screen

screen_url

Read-onlyIdempotent

Deterministic pre-fetch URL & SSRF firewall detecting loopback, RFC1918, CGNAT, IPv6 mapped/unique-local/link-local, AWS/GCP/Azure/Alibaba metadata endpoints, hex/octal/decimal IP encodings, dangerous schemes, embedded credentials, punycode homoglyphs, and open redirects. Requires $0.002 (2000 atomic) Base USDC on eip155:8453 via x402 PAYMENT-SIGNATURE header.

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": "screen_url"
  }
}

Input Schema

Name	Required	Description	Default
`url`	No	Single URL shorthand (up to 2048 chars) to inspect for SSRF, private/metadata IPs, dangerous schemes, credentials, IDN homoglyphs, and open redirects.
`urls`	No	URLs (up to 2048 chars each) to pre-screen before fetch for SSRF (loopback, RFC1918, CGNAT, IPv6 mapped/local, cloud metadata, hex/octal/decimal IP encodings), non-HTTP(S) schemes, credentials, punycode homoglyphs, and open redirects.

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 13, 2026

TDQS

A3.9/5.0

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, closed-world), so the description's real value is the paid-access disclosure: $0.002 USDC on eip155:8453 via an x402 PAYMENT-SIGNATURE header, which an agent must know before calling. It stops short of describing the response shape (verdict vs. findings list) or any rate limits, which matters given there is no output schema.

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?

Two sentences, front-loaded with the purpose and its detection surface, then the payment prerequisite. The threat enumeration is long but earns its place as scannable signal rather than redundant wording.

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

Completeness3/5

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

The payment requirement is disclosed, which is essential for invocation, but with no output schema the description never says what a caller receives back — a boolean verdict, a list of triggered findings, open-redirect targets, or an error shape. For a security-gating tool whose result determines whether an agent may fetch, that is a meaningful omission.

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%, so the two parameters and their 2048-char/25-item limits are already documented in the schema. The description adds no new semantics, and notably never states whether 'url' and 'urls' are mutually exclusive or how the two are combined — a gap the schema does not resolve either.

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+resource ('pre-fetch URL & SSRF firewall') and enumerates exactly what it detects (loopback, RFC1918, CGNAT, cloud metadata endpoints, hex/octal/decimal encodings, punycode homoglyphs, open redirects). This distinguishes it clearly from siblings like screen_domain and screen_address that operate on other input types.

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?

The phrases 'pre-fetch' and 'pre-screen before fetch' imply the usage context is validating a URL before an agent fetches it, which is helpful. However, there are no explicit when-not conditions, no named alternatives among the screen_* siblings, and no guidance on when to use the single 'url' versus the 'urls' array form.

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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