Developers overview

Use these tools to connect B2B Signals to your own code, Zapier, Make, n8n or an AI assistant. You’ll find them in Settings, under API & MCP and Webhooks.

Tool	Use it to	Direction
REST API	Read people, write outreach and run campaigns from your code	You call us
Webhooks	Get told the moment something happens	We call you
MCP	Let an AI tool work in your workspace	Your AI tool calls us

REST API

Send your API key in the X-API-Key header.

curl -H "X-API-Key: $B2B_API_KEY" \
  "$B2B_API_BASE/leads/?limit=10&min_score=80"

Base URL

Find your base URL in Settings › API & MCP. Open REST API. The examples there already include it, ready to copy. Use it as $B2B_API_BASE in the examples on this page. All paths below are relative to it.

First calls

What it does	Call
List your top people. `limit` goes up to 500 and defaults to 50.	`GET /leads/?limit=10&min_score=80`
Get one person’s full detail	`GET /leads/details/{lead_id}`
Write outreach for a person. This sends nothing.	`POST /leads/{lead_id}/outreach`

Permissions

There are no scopes. A key has owner-level access to its one workspace, so treat it like a password. A key works only in its own workspace. Asking for another with the X-Workspace-Id header returns 403. Some actions always need a person signed in, and a key gets 403:

turning on automatic approval or auto-reply that sends by itself,
changing a live campaign’s approval steps,
loosening safety settings,
replying to a person directly from Inbox,
turning on Let AI tools approve and send messages.

Approving messages and resuming someone’s campaign also return 403, unless an owner or admin has turned on Let AI tools approve and send messages. See MCP.

Rate limits

We don’t set a general per-key request limit today. Some actions have their own:

Action	Limit	Answer past the limit
Sending a saved draft reply with a key	30 per workspace per UTC day	`429`
Sending a saved draft reply in a chat with a recent message from you	One every 2 minutes per chat	`429`

Other actions can have limits too, and they answer the same way. Handle 429 by waiting and trying again. If the response has a Retry-After header, wait that long. Sending limits on your senders always apply, however a message is started.

Errors

Status	Meaning	What to do
`401`	The key is missing or wrong, or it was turned off	Check the header, or make a new key
`402`	Sending is paused until your subscription payment goes through	Check billing
`403`	A person must do this, your plan doesn’t include it, or a key tried another workspace	Read `detail` in the response
`404`	It doesn’t exist in this workspace	Check the id
`409`	The state changed, such as a reply that’s out of date	Read `detail`, then fetch the latest state
`422`	The request isn’t valid	Read `detail` for the field
`429`	A limit was reached	Wait and try again

The response body has a detail field. It’s either a sentence or an object with code and message.

Before you build

A key can act on real people. Calls that start a campaign or send a message reach real people on LinkedIn, and sent messages can’t be taken back. Test against a small list first.

API quickstart

Add a person and read results in a few requests.

API keys

Make, replace or turn off your key.

Webhooks

Events, payloads and retries.

MCP

Connect an AI tool.

Integrations

Send people in from another tool.

Build on B2B Signals

API reference

REST API

Base URL

First calls

Permissions

Rate limits

Errors

Before you build

API quickstart

API keys

Webhooks

MCP

Integrations

​REST API

​Base URL

​First calls

​Permissions

​Rate limits

​Errors

​Before you build

​Related

API quickstart

API keys

Webhooks

MCP

Integrations

REST API

Base URL

First calls

Permissions

Rate limits

Errors

Before you build

Related