Which clients does the Qualisend MCP server work with?

Any MCP-compatible client that supports Streamable HTTP transport, including Claude (Team/Enterprise, or Pro custom connectors), ChatGPT (developer mode / connectors), Cursor, VS Code, and others.

Do I need an API key?

No. One-click sign-in over OAuth 2.1 is the recommended path and requires no keys. You can alternatively supply a Qualisend API key as the bearer token.

What data does the connector access?

Only the inputs you pass to a tool — an email address or list, a domain, a raw email header, or an SMTP code — scoped to the workspace you connect. It never accesses your conversations, chat history, assistant memory, or files, and returns only the tool's result.

What tools does it provide?

Twelve tools in three groups: core verification (verify_email, verify_emails, verify_list, get_credit_balance, get_verification), deliverability and authentication (check_domain, generate_dns_record, analyze_email_header, check_disposable, check_typo, lookup_smtp_code), and reputation monitoring (check_blacklist).

How much does it cost?

Verifying an address costs one credit (the same as the REST API); the read tools and every deliverability and blacklist tool are free. A free plan includes 100 credits that never expire. The deliverability tools require the Qualisend Pro plan, and the blacklist check requires the Blacklist Monitoring add-on.

Qualisend MCP server

The Qualisend MCP (Model Context Protocol) server lets an AI agent verify email addresses, clean lists, and run sending-domain deliverability checks through Qualisend — in Claude, ChatGPT, or any MCP-compatible client, with no code and no CSV exports. This page covers how to connect it, how it authenticates, all twelve tools it exposes, and how it handles your data.

Endpoint: https://app.qualisend.com/api/mcp
Transport: Streamable HTTP (JSON-RPC 2.0), stateless
Authentication: OAuth 2.1 (recommended) or a Qualisend API key
Registry name: com.qualisend/email-verification

Requirements

A Qualisend account. The free plan includes 100 verification credits that never expire.
An MCP-compatible client — Claude (Team/Enterprise, or a Pro custom connector), ChatGPT (developer mode / connectors), Cursor, VS Code, or similar.

Connecting the server

Add the endpoint below as a custom connector in your client, then authenticate with one-click sign-in or an API key.

MCP endpoint

https://app.qualisend.com/api/mcp

Option A — Sign in (OAuth 2.1)

Recommended. No keys to copy — your client opens a “Connect Qualisend” page where you log in and approve access to a workspace.

Claude: Settings → Connectors → Add custom connector → paste the endpoint → Connect and approve.
ChatGPT: Settings → Connectors → Add → paste the endpoint → Connect and approve.

Option B — API key

Prefer a static credential? Create a key in your dashboard under Settings → API keys and supply it as the bearer token when you add the connector:

Authorization: Bearer qs_live_…

Once connected, just ask: “verify sales@acme.com”, “are these 10 addresses deliverable?”, or “how many verification credits do I have left?”

Authentication

OAuth uses standard OAuth 2.1 with PKCE and dynamic client registration, so the connection is scoped to the workspace you approve. Access tokens are short-lived (1 hour) and refresh tokens rotate; tokens and authorization codes are stored only as hashes, and redirect URIs are matched exactly. API-key auth uses a bearer token (qs_live_…) in the Authorization header. Either way, auth is an explicit header value — never a cookie or session.

Tools

The server exposes twelve tools, mapped to the same engine as the Qualisend REST API, in three groups. The core verify tools work on any plan (including the free plan); the deliverability tools require the Qualisend Pro plan, and the blacklist check requires the Blacklist Monitoring add-on. Only the three verify_ tools consume credits — everything else is free.

Verify & clean

The core verification tools — available on every plan, including the free plan. The three verify_ tools consume 1 credit per address; the reads are free.

Tool

What it does

Cost

verify_email

Verify one address — syntax, domain/MX, disposable + role detection, typo suggestion, and mailbox reachability — for a deliverable / risky / undeliverable / unknown verdict with a reason code and a 0–100 confidence score. Returns an instant verdict plus a job_id; the SMTP probe finishes a few seconds later.1 credit

verify_emails

emails[] (1–50)

Verify a batch of up to 50 addresses synchronously and get a verdict for each.1 credit each

verify_list

emails[] (1–1,000)

Verify a large list of up to 1,000 addresses asynchronously — creates one job and returns a job_id. Poll get_verification for progress and a result summary.1 credit each

get_credit_balance

—

How many verification credits your workspace has left.Free

get_verification

job_id

Look up a verification's status or result by job_id — the SMTP probe finishes after the instant verdict.Free

Deliverability & authentication

Sending-domain and message diagnostics. No credits used; available on the Qualisend Pro plan.

Tool

What it does

Cost

check_domain

domain

Check whether a domain is set up to reach the inbox — its mail servers (MX) plus SPF and DMARC authentication, and what's missing. A deliverability health check for a sending domain.Free

generate_dns_record

type, domain, …

Generate the exact DNS record a domain needs for email authentication — SPF, DMARC, BIMI, or MTA-STS — ready to copy into DNS, with where to put it.Free

analyze_email_header

raw

Parse a raw email's headers to show the route it took, timing per hop, and whether it passed SPF/DKIM/DMARC and spam checks — to diagnose why a message was slow or went to spam. Paste the message source (“Show original”).Free

check_disposable

Tell whether an address is a throwaway/temporary inbox, a generic role address (info@, support@), or a free consumer address (e.g. Gmail).Free

check_typo

Spot a likely typo in an address's domain (e.g. gmial.com) and suggest the correct one.Free

lookup_smtp_code

code

Explain a mail-server reply/error code (e.g. 550 or 5.1.1) in plain English, and whether it's a temporary hiccup or a permanent failure.Free

Reputation monitoring

No credits used; requires the Qualisend Blacklist Monitoring add-on.

Tool

What it does

Cost

check_blacklist

target

Check whether a sending domain or IP is on any major email blacklist (Spamhaus, SpamCop, Barracuda, and others) — a point-in-time reputation check.Free

A verify_email call returns the instant local verdict plus a job_id; the SMTP mailbox probe finishes a few seconds later, so use get_verification (or just ask again) for the final result on borderline addresses.

What the results look like

Every address returns one of four verdicts — deliverable, risky, undeliverable, or unknown — each with a machine-readable reason code, sub-flags (catch-all, disposable, role, full mailbox), the MX provider, and a 0–100 confidence score. These are the same public fields the REST API returns.

Credits & rate limits

Each verification costs one credit, whether the agent checks one address or a thousand; reads (get_credit_balance and get_verification) are free. The connector uses the same credit balance and rate limits as your REST API access, so you can ask “how many credits are left?” before a large job. The free plan includes 100 credits that never expire.

Security & privacy

The MCP grants exactly what you approve — nothing more.

Scoped to one workspace

Every tool call is authenticated (OAuth token or API key) and scoped to the single workspace you connect. There is no path to another customer's data, to admin functions, or to any internal system beyond the verification flow. The server reuses the same authentication, scope, rate-limit, and credit checks as the public REST API.

Public verdict only

Responses contain only the public verification fields the REST API returns — never internal engine details, probe infrastructure, or SMTP transcripts beyond the deliverability result. The connector receives only the addresses you submit; it never accesses your AI conversations, chat history, assistant memory, or files, and the submitted addresses are never used to train any AI or machine-learning model, nor sold or shared.

No cookies, no CSRF

Authentication is an explicit token or key in the Authorization header — never a cookie or session — so the endpoint has no cross-site (CSRF) surface. OAuth uses PKCE and exact redirect-URI matching, and tokens and codes are stored only as hashes.

Short-lived and revocable

OAuth access tokens are short-lived (1 hour) and refreshes rotate. Revoke access any time by disconnecting the connector in your AI client (OAuth) or revoking the API key in your Qualisend dashboard.

Data handling

Qualisend is an EU-based company and the data you submit is stored and processed in the EU. Verification jobs and their results stay in your workspace until you delete them or close your account; you can delete jobs and results at any time. We do not sell, rent, or share the lists you submit, and we do not use them to train AI or machine-learning models. Full detail — collection, use, retention, third-party processors, and your rights — is in the Privacy Policy, and our security posture is on the Security page.

Revoking access

Disconnect the connector in your AI client to revoke an OAuth connection, or revoke the API key in your Qualisend dashboard under Settings → API keys. OAuth access tokens also expire on their own within an hour.

Support

Questions or issues? Email support@qualisend.com. See also the MCP overview, the Developer API, and the API reference.

Ready to connect?

Start free with 100 credits, then add the endpoint to your client.

Start free MCP overview