Seamless.AI vs Lead411 (2026): Data, Pricing and API Compared

Seamless.AI is the bigger database with the looser API, and Lead411 is the smaller one with buyer intent and a plan you can price. At 1M records a month, neither publishes a number.

Verdict

• Pick Seamless.AI if reps will work in its Chrome extension and dialer, or you need the largest claimed pool of emails and mobile numbers and will take a sales quote (Seamless.AI, September 2026).
• Pick Lead411 if you sell in the US, Canada or northern Europe, want Bombora intent and need a price you can read (Lead411 pricing, September 2026).
• Pick neither if you pull people and company data by API at volume and want one flat monthly bill. LeadOcean is one option, covered below.

Side by side

All figures were checked in September 2026. Both vendors change plans often, so confirm on their pages before you buy.

Data and coverage

Seamless.AI publishes big claims and Lead411 publishes almost none. Seamless.AI lists 2.2B+ verified contacts, 121M+ companies, 1.6B+ verified business emails and 448M+ mobile numbers. These are vendor claims with no stated method, and no count of Lead411 contacts, companies or direct dials is public.

Geography is the clearest difference. Lead411 lists 13 countries (Lead411 FAQ, September 2026). They are the United States, Canada, the UK, Australia, Belgium, Denmark, Finland, Ireland, Luxembourg, the Netherlands, Norway, New Zealand and Sweden. If you sell into Germany, France, Spain or Asia, check that country first.

Seamless.AI states its filter count. Contact search takes 39 filter and modifier parameters and company search takes 23 (Seamless.AI docs, September 2026). Lead411 states no filter count, and its employee search body mixes filters with paging and sort, so we do not count them.

Lead411 adds signals Seamless.AI sells separately. It licenses buyer intent from Bombora, and it tracks hiring trends, funding activity and executive changes (Lead411 FAQ, September 2026; Lead411, September 2026). Seamless.AI also lists buyer intent and job changes, as paid extras (Seamless.AI pricing, September 2026).

API and developer experience

Seamless.AI has the more open API, and Lead411 has the more gated one. Seamless.AI takes a Token header, and a result comes back later by poll or webhook. Lead411 takes an X-API-KEY header, and the API is listed on Ignite and Blaze only.

Seamless.AI: start a research job. It answers HTTP 202 with requestIds. The sample uses placeholder names.

curl -X POST https://api.seamless.ai/api/client/v1/contacts/research \
  -H "Content-Type: application/json" \
  -H "Token: $SEAMLESS_API_KEY" \
  -d '{"contacts":[{"contactName":"Jane Doe","companyName":"Acme Corp","title":"CTO"}]}'

Next you call GET /contacts/research/poll with those IDs, or take the result by webhook. A poll ends in done, error, missing or duplicate (Seamless.AI docs, September 2026). The docs give no job time for a large batch.

Lead411: find an employee by employee_id, email, linkedin_url, or title plus company (Lead411 API docs, September 2026).

curl -X POST "https://api.lead411.com/v3/employee/getEmployeeInformation" \
  -H "X-API-KEY: $LEAD411_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"email":"jane.doe@acme.com"}'

Revealing the record is a separate call, POST /employee/unlock_employee_record, and it draws down an unlock_quota. Lead411 also publishes an OpenAPI 3.1 spec and a Postman collection.

On MCP, Seamless.AI wins on what you can use today. Its hosted server has 57 tools across 13 domains, with OAuth 2.1 or an API key (Seamless.AI MCP docs, September 2026). Lead411's server exists, but it returns 401 until Lead411 Support enables it, and the docs do not list its tools.

Throughput is a real difference. Seamless.AI states 60 requests a minute per endpoint. At 500 records a call, 1,000,000 records is 2,000 search calls and 2,000 research calls, about 34 minutes each in separate windows, plus polling (Seamless.AI docs, September 2026). Lead411 publishes no limit to divide by, so ask before you plan a bulk job.

Pricing

Seamless.AI publishes credits but no dollars, and Lead411 publishes plan prices but no per-record price. Prices below are monthly list first, billed-yearly figures after.

Seamless.AI's pricing page is a quote form. Licenses carry credits. Free has 50 with no refill, Basic 250 a month and Pro 10,000 a month, refreshed on the contract date (Seamless.AI credit docs, September 2026). Subscriptions are annual, and cancelling needs 60 days' notice before renewal or it renews for 12 months (Seamless.AI terms, September 2026).

Lead411 prints its prices. Spark is $49 a month for 1,000 exports, or $490 a year billed yearly for 12,000. Ignite starts at $150 a month, or $1,500 a year billed yearly ($125 a month), with "1000+" exports. Blaze is "Let's Chat", with unlimited exports on annual plans only (Lead411 pricing, September 2026).

At 10,000 records a month

• Seamless.AI: 10,000 contacts x 1 credit = 10,000 credits, which is one Pro license for a month. Starting from a search adds 10,000 / 10 = 1,000 credits. No public price (Seamless.AI docs, September 2026).
• Seamless.AI, missing records: the docs mark a record with no result as missing on poll but do not say whether it is charged. Ask before you budget.
• Lead411: Spark stops at 1,000 exports a month, so 10,000 needs Ignite, from $150 a month. The page shows its cap only as "1000+", and says Ignite's price varies by team size (Lead411 pricing, September 2026). At Spark's list rate of $49 / 1,000 = $0.049 an export, 10,000 x $0.049 = $490. That is a rate, not a plan you can buy.

At this size Lead411 has the only number you can plan around, and it starts at $150. Seamless.AI may cost less or more. You cannot tell until sales quotes you.

At 1M records a month

• Seamless.AI: no public 1M price. 1,000,000 contacts x 1 credit = 1,000,000 credits, or 1,100,000 with a search first. A Pro license holds 10,000 a month, so that is 1,000,000 / 10,000 = 100 licenses, or a bulk pool. Both are quote only (Seamless.AI docs, September 2026).
• Lead411: no public 1M price. The highest public tier is Ignite, and unlimited exports sit on Blaze, priced by quote (Lead411 pricing, September 2026). Spark stops at 1,000 exports a month.

The pricing page sells "exports", while the API meters record reveals against a quota. Lead411 does not document how one maps to the other, so ask before you budget by export (Lead411 API docs, September 2026).

Seamless.AI says invalid emails are refunded automatically (Seamless.AI, September 2026). Lead411 claims 97% verified emails and has no refund line on the pricing page.

Where Seamless.AI wins

• A far larger claimed dataset: 2.2B+ contacts and 448M+ mobile numbers, against Lead411's "millions".
• A search-and-research API with 39 contact filters, open to read, and 57 MCP tools you can switch on.
• A Chrome extension and dialer for reps, plus invalid-email credit back, by its own statement.
• A free license with 50 credits and no clock.

Where Lead411 wins

• Prices you can read: Spark at $49 and Ignite from $150, with a 7-day trial of 50 exports and no card (Lead411 pricing, September 2026).
• Bombora buyer intent, hiring, funding and executive-change signals, plus one-click sync to more than 25 CRMs (Lead411 FAQ, September 2026).
• A published OpenAPI 3.1 spec and Postman collection, and a stated 429 behavior with exponential backoff.
• Technology data on 30,000+ technologies (Lead411, September 2026).

If you need volume through an API

LeadOcean is a data API and MCP server with no credits and no seats. It has no Chrome extension, dialer or CRM. Pro is $499 a month flat, and Free gives 1,000 records one-off with no card. Both get the same REST API and 12-tool MCP server, and POST /v1/exports returns up to 50,000 rows per request (LeadOcean exports docs, September 2026). Compare it on a list you already know, then see pricing.

FAQ