Feranor Resilience

Domain Resilience Check

domain_check_v1

Read-onlyIdempotent

Measures how resilient a public web domain is from the outside and returns a weighted score out of 100, a per-category breakdown, and prioritised findings explaining what to fix first. Use it to audit a domain you do not control, to verify a fix after deployment, or to compare several domains on the same scale. Covers TLS certificate validity and protocol version, HTTP to HTTPS redirection, HSTS, Content-Security-Policy, X-Frame-Options, X-Content-Type-Options, Referrer-Policy, cache directives, response time, DNS redundancy, IPv6 availability, CDN detection and software version disclosure. Everything is read from the public internet: nothing is authenticated, no ports are scanned, and no credentials are needed. Do not use it for private, internal, or localhost hostnames, for IP addresses, or to test a service you need logged-in access to. For a free score without the detailed findings, use domain_check_score_v1 instead. Price: $0.01 per call (x402, USDC on Base). No signup, no API key.

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": {
      "domain": "<domain>"
    },
    "name": "domain_check_v1"
  }
}

Input Schema

Name	Required	Description	Default
`domain`	Yes	Bare domain name, apex or subdomain, for example 'example.com' or 'www.example.com'. Scheme, path, port and query string are ignored if present. IP addresses and private or localhost hostnames are rejected.

Output Schema

Name	Required	Description	Default
`error`	No
`score`	No
`checks`	No
`domain`	No
`noIndex`	No
`success`	No
`noArchive`	No
`evaluatedAt`	No
`requestedDomain`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedJul 30, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false. The description adds valuable context such as 'Everything is read from the public internet: nothing is authenticated, no ports are scanned, and no credentials are needed,' which clarifies the tool's non-intrusive behavior and pricing model. No contradiction with 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 longer than average but every sentence provides distinct value: purpose, use cases, coverage details, access method, exclusions, alternative, and pricing. It is front-loaded with the core purpose and avoids filler, though slightly dense.

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 that an output schema exists and the tool has modest complexity (one parameter), the description covers all necessary context: what it measures, when to use it, safety profile, exclusions, and how it differs from the sibling. Nothing is missing.

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?

The schema already fully describes the single 'domain' parameter with examples and constraints, achieving 100% coverage. The description reinforces the public-only scope but does not add new parameter-level details, so baseline 3 is appropriate.

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 opens with a specific verb and resource: 'Measures how resilient a public web domain is from the outside' and clearly lists outputs (weighted score out of 100, per-category breakdown, prioritised findings). It also distinguishes itself from the sibling tool by noting 'domain_check_score_v1' provides a free score without detailed findings.

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?

Explicit use cases are given: 'audit a domain you do not control, verify a fix after deployment, or compare several domains.' It also states exclusions ('Do not use it for private, internal, or localhost hostnames, for IP addresses...') and points to an alternative tool for a simpler score. This is comprehensive guidance.

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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