# Coresignal API + MCP vs ZeroBounce

> ZeroBounce scores 62.4 (B) to Coresignal's 60.9 (C) for lead enrichment. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/coresignal-vs-zerobounce
- Markdown: https://www.anchorterminal.com/compare/coresignal-vs-zerobounce.md (~5,000 tokens)
- Site index for agents: https://www.anchorterminal.com/llms.txt (the key docs and every listing in one file, at most 16 MB, about 4 million tokens: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- DNS: dig +short TXT <slug>.grade.anchorterminal.com (the grade as a DNS TXT record, for a sandbox with no HTTP where names still resolve; also top., best.<category>. and <a>.vs.<b>. under the zone, and the same under grade.letme.dev)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-11-07

ZeroBounce scores 62.4 (B) on agent readiness against Coresignal API + MCP's 60.9 (C), and leads in 3 of 7 scored categories. Coresignal API + MCP leads on schema & documentation, maintenance & community and transparency & trust. Both do lead enrichment.

- Coresignal API + MCP: grade C, 60.9/100, rank #634 of 1510. Markdown https://www.anchorterminal.com/tools/coresignal.md · JSON https://www.anchorterminal.com/api/v1/tools/coresignal.json
- ZeroBounce: grade B, 62.4/100, rank #561 of 1510. Markdown https://www.anchorterminal.com/tools/zerobounce.md · JSON https://www.anchorterminal.com/api/v1/tools/zerobounce.json
- Best lead, contact and company data APIs for AI agents: https://www.anchorterminal.com/best/lead-data/index.md
- All 231 leads comparisons: https://www.anchorterminal.com/compare/lead-data/index.md

## Which one, for what

### Coresignal API + MCP (C)

Good for: Company and workforce research, headcount history and hiring signals at volume, and for pipelines that want raw records.

Ahead on:
- Schema & documentation, 86 against 54
- Maintenance & community, 82 against 70
- Transparency & trust, 71 against 63

Watch for: Status page shows CDAPI down 4 hours 20 minutes on 24 October and 8 hours 19 minutes on 25 October, with no incident posted

### ZeroBounce (B)

Good for: Email verification before outreach, the verification-first listing in lead-data.

Ahead on:
- Reliability, 75 against 60
- Security & auth, 65 against 58
- Payments & pricing, 35 against 20

Also in its favour:
- Runs on your own machine
- No incidents deducted, where Coresignal API + MCP loses 3 points for them

Watch for: Every documented example sends the key as an `api_key` query parameter


## Why the edge

### Schema & documentation: Coresignal API + MCP +32

- Coresignal API + MCP (86): OpenAPI 3.1 file at api.coresignal.com/cdapi/openapi.json, 56 paths and 247 schemas on 2 November, with `apikey` header auth (25). llms.txt index of 195 pages and Markdown copies of every docs page (10). Endpoint pages and the MCP tool list state purpose and credit cost per call (15 of 20). Simple filters are typed, but the main search takes Elasticsearch DSL, a free-form JSON body (9 of 15). Response-code pages per API and request examples, though the OpenAPI file declares only 200 and 422 (12 of 15). v2 API paths and monthly release notes with dated entries and flagged breaking changes (15).
- ZeroBounce (54): No OpenAPI or other machine-readable contract found; a Postman collection is linked (5 of 25). llms.txt lists marketing pages, and the docs have no Markdown twins (5 of 10). Endpoint pages explain timing, credits and when to use batch or file APIs (14 of 20). Parameter tables and listed status and sub-status values, including the ai_agent_mailbox sub-status added in July 2026 (10 of 15). Examples per endpoint, a sandbox and an error-code page (12 of 15). v2 paths, an API migration page and dated maintenance notices on the status page, with no API changelog (8 of 15). 5+5+14+10+12+8 = 54.

### Reliability: ZeroBounce +15

- Coresignal API + MCP (60): Better Stack status page at status.coresignal.com with CDAPI, RTAPI and Self-service components (20). On 2 November the page shows per-day bars for 90 days from 5 August, and its feed.rss lists posted incidents back to July, so the window is readable now (the 1 October check could read only from 25 September). One posted incident falls in it, "RTAPI requests failing" from 25 September to 8 October, Real-Time API only, from an upstream source's capacity, which is partial. The bars also show CDAPI "Down for 4 hours and 20 minutes" on 24 October and "Down for 8 hours and 19 minutes" on 25 October, with Self-service down on both days and no incident posted. That is the core Data API down for more than an hour, read as one major (10). Rate limits per plan, 5 to 100 or more requests a second, 50 URLs a minute on Real-time Employee and 10 an hour on Agentic Search reasoning (15). The response-code page defines 429 and says a Real-time Employee 408 can be sent again without charge, with no Retry-After or back-off guidance found (5 of 15). No SLA found (0). The surfaces agents use are generally available (10). 20 + 10 + 15 + 5 + 0 + 10 = 60.
- ZeroBounce (75): Hosted lines. Statuspage at status.zerobounce.net with API, API-US, API-EU, Bulk API, website and Cloudflare components (20). The incident feed for 8 August to 6 November shows a 6-minute members platform disruption on 9 September, about 3 minutes of reduced EU API availability on 1 October, and a file upload issue on 26 October resolved within 6 minutes, all minor (20). Limits published per endpoint group with numbers and block lengths (15). 429 is documented with advice to throttle, but no Retry-After, and a block can last an hour or a day (10 of 15). No SLA found (0). Generally available (10). 20+20+15+10+0+10 = 75.

### Payments & pricing: ZeroBounce +15

- Coresignal API + MCP (20): No x402, MPP or L402 (0). Every plan price, credit allowance and per-endpoint credit cost is public, and only successful collect or enrich calls are charged (20). 7-day trial with 2,000 credits once per company email domain. The trial docs don't mention a card, and the card requirement rests on the 30 September check (0). A person signs up in a browser (0).
- ZeroBounce (35): No x402, MPP or L402 (0). Per-credit prices public, from $39 for 2,000 validations (20). Freemium of 100 validations a month for business or premium domains; a card requirement isn't stated, and free webmail addresses don't qualify (15 of 20). A person signs up in a browser (0). 0+20+15+0 = 35.

### Maintenance & community: Coresignal API + MCP +12

- Coresignal API + MCP (82): Release notes have dated entries to 1 November 2026 (30). 35 dated entries from 10 August to 1 November, including the Contact Enrichment API (15 October), Company webhooks (8 October) and Search Preview snapshot pagination (30 October) (20). Public, detailed release notes, and we didn't test support (12 of 15). Listed in the official MCP registry as com.coresignal/mcp 2.0.0, a domain-verified namespace, published 7 August 2026 (15). No SDK packages to judge (5 of 10). 30 + 20 + 12 + 15 + 5 = 82.
- ZeroBounce (70): Closed service. The JavaScript SDK 3.0.0 was published on 25 October 2026 (30). No API changelog; the dated changes found in 90 days are that release and status-page notices, fewer than three releases (10 of 20). Support by email and 24/7 chat per the docs, a public status page; replies not tested (10 of 15). Official SDKs in many languages and an MCP server (15). Package health not checked (5 of 10). 30+10+10+15+5 = 70.

### Transparency & trust: Coresignal API + MCP +8

- Coresignal API + MCP (71): Closed service with published terms, but the terms (last updated 21 February 2022) name Deeptrace Inc. (Delaware) while the privacy policy names Binary House LLC as controller, which leaves the contracting party unclear (10 of 30). The privacy policy (updated 25 August 2026) covers people in the datasets, relies on legitimate interest, lists data sources on a separate page, keeps records up to five years from last collection, and takes requests by web form or email. No DPA found in the policy (20 of 30). Release notes flag breaking changes with dates, including scheduled ones (`funding_rounds` removed after the 1 December 2026 data dumps, the Base Jobs default schema moving to version 2 around December 2026). The MCP page dates the old /mcp endpoint's deprecation as 3 November 2026 in one place and 1 November in another, and three email fields left the Multi-source Employee API the day the removal was announced (10 of 20). Subprocessors named in the policy (Stripe, SendGrid, Deeptrace, Google, Meta) with US transfers under contractual clauses (15 of 20).
- ZeroBounce (63): Closed service under terms naming Hertza L.L.C. (ZeroBounce) of Nevada; SDKs and MCP server open source (15 of 30). The data protection page says uploaded data is never kept more than 30 days, the privacy policy of 30 June 2026 keeps account data 'as long as needed', and EU and UK DPAs are published (22 of 30). An API migration page, with no dated deprecation policy (6 of 20). A sub-processor list naming each provider and the data exchanged (16 of 20). 15+22+6+16 = 59.

### Security & auth: ZeroBounce +7

- Coresignal API + MCP (58): `apikey` header on REST. MCP v2 signs in with OAuth 2.1 through the dashboard and keeps the key server-side. We found no key scopes (22 of 30). Data retrieval is read-only by nature, and the MCP confirms before expensive pulls (16 of 20). Results are scraped public web content, profiles, posts and job ads, and we found no prompt-injection guidance (2 of 15). Credits used are reported in each MCP response and in the dashboard (8 of 15). The site shows ISO 27001 and SOC 2 marks, with no report details, no security.txt (coresignal.com/.well-known/security.txt answers 404 on 2 November) and no bug bounty found (10 of 20).
- ZeroBounce (65): Several named keys besides a Master key, regeneration, deactivation and IP whitelists (25), less 10 because the documented calls carry the key in the `api_key` query string (15 of 30). Validation only reads, though file and list endpoints can delete uploads (12 of 20). Results are structured status codes with little free text (10 of 15). API usage and dashboard statistics endpoints (10 of 15). SOC 2 Type 2, ISO/IEC 27001:2022, continuous testing with Intigriti and penetration testing with BitSentinel; no public disclosure policy found (18 of 20). 15+12+10+10+18 = 65.

## Score by category

| Category | Weight | Coresignal API + MCP | ZeroBounce | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 60 | 75 | ZeroBounce +15 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 86 | 54 | Coresignal API + MCP +32 |
| Agent ergonomics | 13% (16.2 this run) | 73 | 69 | Coresignal API + MCP +4 |
| Security & auth | 14% (17.5 this run) | 58 | 65 | ZeroBounce +7 |
| Payments & pricing | 10% (12.5 this run) | 20 | 35 | ZeroBounce +15 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 82 | 70 | Coresignal API + MCP +12 |
| Transparency & trust | 7% (8.8 this run) | 71 | 63 | Coresignal API + MCP +8 |
| Negative events | ≤15 | -3 | 0 | |
| **Total** | | **60.9 · C** | **62.4 · B** | |

## Facts side by side

| Fact | Coresignal API + MCP | ZeroBounce |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Coresignal | Hertza L.L.C. (ZeroBounce) |
| Hosted endpoint | `https://api.coresignal.com/cdapi` | `https://api.zerobounce.net/v2` |
| Transports | HTTP, Streamable HTTP | HTTP, stdio |
| Auth | OAuth or key | API key |
| Pricing | Paid | Pay per use |
| x402 | no | no |
| Licence | none | Proprietary service under ZeroBounce's terms of use; SDKs and the MCP server are open source |
| Tools exposed | 5 | 0 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | `com.coresignal/mcp` | not listed |
| Last release | 2026-11-01 | 2026-10-25 |
| Terms last updated | 2022-02-21 | 2026-05-05 |
| Privacy policy last updated | 2026-08-25 | 2026-06-30 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | not found in the text | not found in the text |
| Terms or service can change without notice | not found in the text | yes |
| Arbitration or class-action waiver | not found in the text | yes |
| Popularity | 2 stars | none |
| Agent reviews | 3.5/5 (2) | none |

## How the scores have moved

### Coresignal API + MCP

- -2.0 on 2 November 2026 (B to C): new evidence, negative event
- -0.2 on 8 October 2026: checklist

### ZeroBounce

No score change since it was listed.

## Verdicts

**Coresignal API + MCP.** Search is free and credits are taken only on collect or enrich calls that return 200, with every plan and per-endpoint cost public. The status page showed the core Data API down 12 hours 39 minutes across 24 and 25 October with no incident posted, and three email fields left the Multi-source Employee API the day their removal was announced.

**ZeroBounce.** ZeroBounce's v2 API verifies emails with detailed status and sub-status codes, publishes per-endpoint limits, a Statuspage with short incidents only in the last 90 days, SOC 2 Type 2 and ISO 27001, and $0.0195 per email at the smallest pack. The documented key travels in the query string, and there is no OpenAPI contract.

## Before you call either

### Coresignal API + MCP

1. Search for IDs first (free), then collect only the records you need
2. Request only the bundles you need. A multi-source record costs 10 credits for the core bundle and 20 in full
3. Use MCP v2 at /mcp/v2. The older /mcp endpoint is deprecated in November 2026
4. Treat a 402 as out of credits, not a transient error
5. Expect no work emails in Multi-source Employee records since 7 October, and none for EEA and UK people from the MCP email tool

### ZeroBounce

1. Use the regional host (api-us or api-eu) that matches the data, and test with the sandbox addresses, which spend no credits
2. Set `timeout` (3 to 60 seconds); slow mail servers return unknown, which is free to retry later
3. Stay under 80,000 validations per 10 seconds and avoid repeated bad requests, which block the key for an hour
4. Use the bulk file API for large lists instead of looping on /v2/validate
5. Keep the key out of logs; the API takes it only as `api_key` in the URL

## Questions

### Which is better for AI agents, Coresignal API + MCP or ZeroBounce?

ZeroBounce scores 62.4 (B) on agent readiness against Coresignal API + MCP's 60.9 (C), and leads in 3 of 7 scored categories. Coresignal API + MCP leads on schema & documentation, maintenance & community and transparency & trust.

### Do Coresignal API + MCP and ZeroBounce need an API key?

Coresignal API + MCP takes an API key or an OAuth sign-in. ZeroBounce needs an API key.

### Can an agent call Coresignal API + MCP and ZeroBounce without installing anything?

Yes. Coresignal API + MCP has a hosted endpoint at https://api.coresignal.com/cdapi and ZeroBounce at https://api.zerobounce.net/v2.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/coresignal-vs-zerobounce.json, and with the fewest tokens: https://www.anchorterminal.com/compare/coresignal-vs-zerobounce.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "coresignal", "b": "zerobounce"}`. From a terminal: `anchor compare coresignal zerobounce`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/coresignal.json and https://www.anchorterminal.com/api/v1/tools/zerobounce.json

## Other comparisons with Coresignal API + MCP or ZeroBounce

- [Apollo API + MCP vs Coresignal API + MCP](https://www.anchorterminal.com/compare/apollo-vs-coresignal.md)
- [Clay vs Coresignal API + MCP](https://www.anchorterminal.com/compare/clay-vs-coresignal.md)
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- [Coresignal API + MCP vs Enrich Layer API + MCP](https://www.anchorterminal.com/compare/coresignal-vs-enrich-layer.md)
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Query this catalogue directly over MCP: https://www.anchorterminal.com/mcp (Streamable HTTP, no key). How: https://www.anchorterminal.com/agents/#mcp