ShieldAPI MCP

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shieldapi.check_url

Read-onlyIdempotent

Check URLs for malware, phishing, and security threats using URLhaus database and heuristic analysis to identify potentially dangerous links.

Instructions

Check a URL for malware, phishing, and other threats. Uses URLhaus + heuristic analysis.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`url`	Yes	The URL to check (e.g. https://example.com)

Implementation Reference

src/index.ts:179-186 (handler)

The handler for 'shieldapi.check_url' is dynamically registered in a loop that iterates over the `TOOLS` object. The handler invokes `callShieldApi` with the 'check-url' endpoint.

for (const [name, def] of Object.entries(TOOLS)) {
  server.tool(
    name,
    def.description,
    { [def.param]: z.string().describe(def.paramDesc) },
    { ...readOnlyAnnotations, title: TOOL_TITLES[name] || name },
    async (params) => formatResult(await callShieldApi(def.endpoint, params as Record<string, string>))
  );

src/index.ts:32-37 (registration)

Definition of the 'shieldapi.check_url' tool configuration.

'shieldapi.check_url': {
  description: 'Check a URL for malware, phishing, and other threats. Uses URLhaus + heuristic analysis.',
  param: 'url',
  paramDesc: 'The URL to check (e.g. https://example.com)',
  endpoint: 'check-url',
},

Schema Changelog

Changes observed during successful MCP inspections.

First observedv3.0.0Mar 24, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds value by disclosing the underlying analysis sources (URLhaus + heuristic analysis) and the specific threat categories (malware, phishing, other threats), which provides behavioral context beyond the annotations.

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?

The description is two concise sentences, front-loaded with the core action ('Check a URL...') and a short secondary sentence on methodology. No unnecessary words or repetition.

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?

For a simple read-only tool with one parameter, the description covers purpose, method, and threat scope. There is no output schema, so the description could theoretically mention the return format, but the tool is simple enough that this omission is not a major gap.

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% with the 'url' parameter well-described ('The URL to check (e.g. https://example.com)'). The tool description adds minimal extra parameter meaning—it only repeats 'URL'—so a baseline score of 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 clearly states the action 'Check a URL' and the specific purpose 'for malware, phishing, and other threats'. This distinguishes it from sibling tools like check_domain, check_email, or check_ip by explicitly targeting URLs.

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 description clearly sets the context by specifying a URL as the input type, and mentions the analysis method (URLhaus + heuristics). It does not explicitly name alternatives or state when not to use it, but the scope is clear enough for an agent to select this tool for URL checks.

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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