UserCheck API
67
AI ReadinessAI-Aware (B+)67/100
Official vendor OpenAPI document · agent-readyCommunicationsEmail Deliverybearer8 EndpointsREST
For Agents
Programmatically validate email address, validate domain. Covers 8 operations with bearer authentication.
Use for: I need to validate email address, I want to validate domain, Search for add domain to blocklist, Find all blocklisted domains
Not supported: Does not handle payments, crm, or developer tools - use for communications only.
An API designed to help businesses and developers detect and block disposable (temporary) email addresses. The API exposes 8 endpoints secured with bearer authentication.
Install Jentic One Beta
Connect the UserCheck API to your agent
Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the UserCheck API, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.
Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.
1
Step 1: Jentic One Host machine
# On the machine that will host your Jentic One instance:
curl -fsSL "https://jentic.com/install.sh?src=apis&api=%2Fapis%2Fusercheck.com%2Fusercheck" | sh2
Step 2: Agent machine
# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL "https://jentic.com/install.sh?src=apis&api=%2Fapis%2Fusercheck.com%2Fusercheck" | sh
jentic register # connects your agent to your Jentic One instanceJentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.
Capabilities
What an agent can do with UserCheck API.
Validate email address
Add domain to blocklist
List blocklisted domains
Bulk add domains to blocklist
Check domain blocklist status
Remove domain from blocklist
Use Cases
Patterns agents use UserCheck API for, with concrete tasks.
★ Communications Operations
Use the UserCheck API to perform communications operations programmatically. The API provides 8 endpoints covering core functionality including validate email address, validate domain, add domain to blocklist.
Call GET /email/{email} to validate email address
Automated blocklist Management
Automate blocklist operations by combining multiple UserCheck API endpoints. Agents can validate domain and then add domain to blocklist in a single workflow.
Call GET /domain/{domain} to validate domain, then verify the result
AI Agent Integration via Jentic
AI agents discover and call UserCheck API endpoints through Jentic without managing credentials directly. An agent searches for the required operation by intent, receives the matching endpoint schema, and executes the call with Jentic-managed authentication. This eliminates the need to read API documentation or handle bearer tokens manually.
Search Jentic for 'validate email address', load the operation schema, and execute with Jentic-managed credentials
Key Endpoints
8 endpoints — an api designed to help businesses and developers detect and block disposable (temporary) email addresses.
METHOD
PATH
DESCRIPTION
GET
/email/{email}
Validate email address
GET
/domain/{domain}
Validate domain
POST
/blocklist
Add domain to blocklist
GET
/blocklist
List blocklisted domains
POST
/blocklist/bulk
Bulk add domains to blocklist
GET
/blocklist/{domain}
Check domain blocklist status
DELETE
/blocklist/{domain}
Remove domain from blocklist
GET
/status
Get API status
GET
/email/{email}
Validate email address
GET
/domain/{domain}
Validate domain
POST
/blocklist
Add domain to blocklist
GET
/blocklist
List blocklisted domains
POST
/blocklist/bulk
Bulk add domains to blocklist
GET
/blocklist/{domain}
Check domain blocklist status
DELETE
/blocklist/{domain}
Remove domain from blocklist
GET
/status
Get API status
Jentic AI Readiness Score
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.
U
UserCheck API
- AI-Aware (B+)67/100
87
Foundational Compliance63
Developer Experience & Jentic Compatibility50
AI-Readiness & Agent Experience94
Agent Usability60
Security78
AI DiscoverabilityPowered by JenticScoring Framework 1.0.0 | Scoring Engine 0.4.0
Show dimension breakdown
87
Foundational Compliance
Base layer of spec validity and structural soundness.
Grade: ASignals: 4
98%
Lint Results
Aggregated quality score from linter diagnostics, weighted by severity.
100%
Resolution Completeness
Percentage of `$ref` references that resolve successfully.
100%
Specification Validity
Checks whether the API description parses successfully and conforms to its declared specification (e.g., OpenAPI).
50%
Structural Integrity
Structural correctness score based on schema issues using logarithmic dampening.
63
Developer Experience & Jentic Compatibility
Clarity, completeness, and ingestion readiness for developers and tooling.
Grade: B-Signals: 4
0%
Example Density
How richly the API is illustrated with examples.
100%
Example Validity
Percentage of examples that conform to their schemas.
50%
Response Coverage
Percentage of operations with complete response definitions (success, client error, server error).
100%
Tooling Readiness
Health of API ingestion, bundling, and resolution within Jentic pipelines.
50
AI-Readiness & Agent Experience
Semantic breadth, depth, and agent comprehension for AI systems.
Grade: C-Signals: 4
44%
Description Coverage
Coverage of descriptions across API elements.
0%
Error Standardization
Coverage of RFC 9457 Problem Details for error responses.
100%
OperationId Quality
Coverage, uniqueness, and casing consistency of operationIds for AI inference.
57%
Summary Coverage
Coverage of summaries across operations/tags/info.
94
Agent Usability
Functional utility, complexity comfort, and AI orchestration readiness.
Grade: A+Signals: 1
94%
Complexity Comfort
Agent comfort level based on API operational and structural complexity.
60
Security
Trust, risk posture, and security compliance.
Grade: B-Signals: 1
60%
Authentication Strength
Average quality of security schemes based on authentication method strength (weakest link for OAuth2).
78
AI Discoverability
Findability, semantic richness, and reasoning readiness.
Grade: A-Signals: 1
78%
Descriptive Richness
Clarity and depth of descriptions across API elements.
Score it yourself
Every API in the directory is allowlisted, so you can re-score it with no key required.
npx @jentic/api-scorecard-cli score <openapi-url>Why Jentic?
What agents get from Jentic-routed access to this vendor.
Setup
Wiring the UserCheck API by hand means attaching its bearer token, encoding the email or domain into the path, and maintaining your blocklist through separate calls yourself. Through Jentic you install once, import UserCheck from the API Directory, store the token once, and your agent calls it.
Permission scoping
UserCheck puts the domain in the URL path (/blocklist/{domain}), so a rule can pin your agent to one domain's blocklist entry: it can read that entry if you allow it. You choose the operations it may call, so blocklist deletion is not included unless you add it.
Credential isolation
Your UserCheck token 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.
Intent-based discovery
Agents search Jentic by intent such as 'validate an email address' or 'check a domain', and Jentic returns the matching UserCheck operation with its input schema so the agent calls the right endpoint without browsing the reference docs.
Related APIs
Alternatives and complements available in the Jentic catalogue.
FAQs
Specific to using UserCheck API through Jentic.
What authentication does the UserCheck API use?
The UserCheck API uses a Bearer token in the Authorization header. Through Jentic, these credentials are stored encrypted in your Jentic One instance and injected at execution time, so raw secrets never enter the agent context.
Can I validate email address with the UserCheck API?
Yes. Use the GET /email/{email} endpoint. The API returns structured JSON responses that agents can parse and act on directly.
What are the rate limits for the UserCheck API?
Rate limits are not specified in the OpenAPI spec. Check the vendor documentation for current limits. Through Jentic, rate limiting is handled automatically with retry logic built into the execution layer.
How do I validate email address through Jentic?
Install the Jentic SDK with pip install jentic, authenticate through Jentic One, the self-hosted execution layer, then search for 'validate email address'. Jentic returns the matching UserCheck API operation with its input schema. Load the schema and execute the call - credentials are injected automatically.
How many endpoints does the UserCheck API have?
The UserCheck API exposes 8 endpoints covering blocklist, domain, email operations.
Can I limit what my agent is allowed to do with the UserCheck API?
Yes. Because you self-host Jentic One, your own rules decide which UserCheck operations and credentials the agent may use, so you can allow read-only checks like GET /email/{email} and GET /domain/{domain} while excluding blocklist writes such as POST /blocklist or DELETE /blocklist/{domain}. Since UserCheck puts the domain in the URL path (/blocklist/{domain}), you can pin the agent to a single domain's blocklist entry and grant only the ability to read it. Destructive operations like removing a domain from the blocklist stay off unless you explicitly add them to what the agent can call.
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