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NsLookup-io

nslookup.io MCP Server

by NsLookup-io

ssl_certificate

Check SSL/TLS certificate details for any domain including issuer, expiry date, validity, cipher strength, and protocol version.

Instructions

Check the SSL/TLS certificate for a domain. Returns issuer, expiry date, days until expiry, certificate chain validity, cipher strength, SAN domains, fingerprint, and TLS protocol version.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
domainYesDomain name to check SSL certificate for (e.g. github.com)

Implementation Reference

  • Handler function for the ssl_certificate tool which calls the /v1/certificates/check API endpoint.
    async ({ domain }) => {
      try {
        const result = await apiPost(
          "/v1/certificates/check",
          { domain },
          { prefix: "/portal-api", timeout: 15000 }
        );
        return { content: [{ type: "text", text: formatJson(result) }] };
      } catch (error) {
        return {
          content: [
            {
              type: "text",
              text: `Error: ${error instanceof Error ? error.message : String(error)}`,
            },
          ],
          isError: true,
        };
  • src/tools.ts:214-219 (registration)
    Registration of the ssl_certificate tool with its schema definition.
    server.tool(
      "ssl_certificate",
      "Check the SSL/TLS certificate for a domain. Returns issuer, expiry date, days until expiry, certificate chain validity, cipher strength, SAN domains, fingerprint, and TLS protocol version.",
      {
        domain: z.string().describe("Domain name to check SSL certificate for (e.g. github.com)"),
      },
Behavior3/5

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

With no annotations provided, the description carries the full burden. It discloses the return data (issuer, expiry date, etc.) and implies a read-only operation, but lacks details on error handling, rate limits, authentication needs, or network dependencies. It adds value by specifying output content but misses key behavioral traits.

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 front-loaded with the core purpose in the first sentence, followed by a concise list of return values. Every sentence earns its place, with no wasted words, making it efficient and easy to parse.

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?

Given the tool's moderate complexity (single parameter, no output schema, no annotations), the description is adequate but incomplete. It covers the purpose and output semantics well, but lacks usage guidelines and behavioral details like error cases or performance expectations, leaving gaps for an agent.

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 schema already documents the single 'domain' parameter. The description adds no additional parameter details beyond what the schema provides, such as format examples or constraints, meeting the baseline for high schema coverage.

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 specific action ('Check the SSL/TLS certificate for a domain') and the resource ('domain'), distinguishing it from sibling tools like dns_lookup, security_scan, or uptime_check by focusing exclusively on SSL/TLS certificate inspection.

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

Usage Guidelines2/5

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

No guidance is provided on when to use this tool versus alternatives. While the purpose is clear, there's no mention of prerequisites, limitations, or comparisons to sibling tools like security_scan, which might overlap in functionality.

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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