canonical: https://jentic.com/apis/domain-sentinel.com/domain-sentinel # Domain Sentinel API The Domain Sentinel API returns availability and registration data for a domain from a single lookup endpoint. It resolves each domain through RDAP where the TLD has a registered server, falls back to WHOIS on port 43 for curated registries, and uses a DNS delegation check otherwise, so the result reflects the most authoritative source available. Calls work anonymously under a low rate limit or with an API key that counts toward a monthly plan quota reported in the response headers. ## For AI agents Check whether a domain is available or registered and read its registration data, sourced from RDAP, WHOIS, or a DNS delegation check. ## Scope Does not register domains, configure DNS records, or host websites. Use for domain availability and registration-data lookups only. ## Capabilities - Check whether a domain is available to register or already taken - Read registration data for a domain from RDAP, WHOIS, or a DNS delegation check - Look up domains anonymously or with an API key that raises the monthly plan quota ## Use cases ### Agent domain availability checks An AI agent connected through Jentic checks domain availability on demand while brainstorming product or brand names, reporting for each candidate whether it is free to register or already taken. The agent reads the lookup result and its registration source so a human sees an answer backed by RDAP or WHOIS data rather than a guess. Example prompt: Check whether example-brand.com is available and report its availability and registration source ### Domain research across a candidate list Teams researching a naming shortlist call the lookup endpoint once per candidate to build a table of which domains are free and which are registered. Because each call returns the registration source and status, the results are auditable against the authoritative registry rather than a cached guess. Example prompt: For a list of five candidate domains, look up each one and return which are available and which are registered ### Registration data lookup Trust and operations teams look up a domain's registration data to see its registrar, status, and registration dates before acting on mail or links from it. The endpoint returns registration details sourced from RDAP or WHOIS, giving an agent a factual basis for a decision. Example prompt: Look up a domain and return its registrar, status, and registration source ## Key resources - **Lookup** — Resolve a single domain to availability and registration data via RDAP, WHOIS, or a DNS delegation check ## AI readiness This API is usable in Jentic One now. Its AI-readiness score against Jentic's framework shows where it stands today and where improvements would make it even easier for agents to use. - **Score:** 46 / 100 - **Maturity:** Foundational - **Dimensions:** - Foundational Compliance: 100 / 100 - Developer Experience & Jentic Compatibility: 73 / 100 - AI-Readiness & Agent Experience: 20 / 100 - Agent Usability: 94 / 100 - Security: 60 / 100 - AI Discoverability: 63 / 100 - **View full report:** https://jentic.com/apis/domain-sentinel.com/domain-sentinel/scorecard - **How the score is calculated:** https://docs.jentic.com/reference/api-readiness-framework/overview/ - **More about the dimensions:** https://docs.jentic.com/reference/api-readiness-framework/specification/#dimensional-model-overview ### Score it yourself Every API in the directory is allowlisted, so you can re-score it with no key required. - **Score your own API:** https://jentic.com/scorecard.md - **Scoring CLI agent skill:** https://github.com/jentic/jentic-api-scorecard/blob/main/skills/jentic-api-scorecard/SKILL.md ```sh npx @jentic/api-scorecard-cli score ``` ## Why Jentic - **Setup:** Wiring Domain Sentinel by hand means handling its optional Bearer token, tracking the plan quota returned in the response headers, and backing off the anonymous rate limit yourself. Through Jentic you install once, import Domain Sentinel from the API Directory, store the key once, and your agent calls it. - **Permission scoping:** Domain Sentinel exposes a single read-only lookup operation, so a rule can allow your agent that lookup and nothing else. There are no write or delete operations to grant, so the agent can only read availability and registration data. - **Credential handling:** Your Domain Sentinel key, when you use one, is stored once, encrypted, by your own Jentic One instance and injected at execution time. It never enters the agent's prompt, logs, or context. - **Discovery method:** Agents search Jentic by intent such as 'check domain availability', and Jentic returns the matching Domain Sentinel operation with its input schema so the agent calls the right endpoint without browsing the reference docs. ## Related APIs - **IP2WHOIS** — WHOIS domain lookups returning registrant and registrar data, an alternative source to Domain Sentinel. - **DomainsDB** — Searches a database of known registered domains, versus Domain Sentinel's live per-domain lookup. - **Cloudflare** — DNS and domain management that pairs with Domain Sentinel's availability and registration lookups. ## FAQ ### What authentication does the Domain Sentinel API use? The Domain Sentinel API accepts an optional Bearer token, your API key, per its OpenAPI spec. Calls also work anonymously under a lower rate limit, and a key raises your monthly quota, which is reported back in the response headers. Through Jentic the key is stored once and injected at call time so it never enters the agent's prompt. ### Can I check domain availability with the Domain Sentinel API? Yes. The lookup endpoint returns whether a domain is available or registered along with its registration data, resolved through RDAP, WHOIS, or a DNS delegation check depending on the TLD. ### What are the rate limits for the Domain Sentinel API? Anonymous callers are limited per the spec to a few requests per minute and a small daily cap. Adding an API key raises your allowance to the monthly quota set by your plan, and the remaining quota is returned in the response headers on each call. ### Is there a Domain Sentinel API MCP server? You don't need an MCP server to give your agent the Domain Sentinel API. Jentic connects it directly from the API Directory: import it, store your key once, and your agent calls the lookup it needs without loading another server's tool definitions into its context. ### Can I limit what my agent is allowed to do with the Domain Sentinel API? Yes. The API exposes one read-only lookup, so a rule can allow your agent that single operation and deny everything else, and each call it makes is logged for review. ### How do I check a domain with the Domain Sentinel API through Jentic? Search Jentic for 'check domain availability', add the Domain Sentinel API from the directory, and store your key once; your agent can then look up any domain's availability and registration data on demand. To run it on your own infrastructure, install Jentic One from its GitHub repo.