Claude Tag (Slack)

Use Nansen data directly inside Slack by connecting the Nansen MCP server to Claude Tag — Anthropic's native Slack integration. Once set up, any Slack channel can query Nansen without leaving the conversation.

Prerequisites

• A Nansen API key — get yours at app.nansen.ai/api

• Admin access to your Anthropic org's Claude Tag settings

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Step 1 — Switch Claude in Slack to New mode

Go to claude.ai/admin-settings/claude-tag and make sure the Claude in Slack version dropdown (top-right of the page) is set to New.

Legacy mode must be switched off first. While on Legacy, the Access bundles and Connections sections are hidden and any credential you add won't be applied.

Legacy mode: settings are saved but won't apply until you switch to New

After switching to New: Access bundles section is now active

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Step 2 — Add the Nansen API credential

From the Claude Tag sidebar, go to Access Bundle and create a new bundle or select an existing bundle you'd like to use. Open the Credentials tab and click + Connect another app.

Access Bundle menu — create a new bundle or select an existing one

Credentials tab — click "+ Connect another app"

Fill in the form as follows:

Field	Value	Notes
Name	Nansen	Any label works
Credential type	Bearer	Required to unlock the Custom headers field
Allowed websites	mcp.nansen.ai	Credential is sent only to this host
Custom headers — Name	NANSEN-API-KEY
Custom headers — Prefix	(leave blank)	Pre-filled with "e.g. Bearer" — clear it
Custom headers — Value	<your Nansen API key>	Paste your Nansen API key here
Custom headers — Name	Accept
Custom headers — Prefix	(leave blank)
Custom headers — Value	application/json, text/event-stream
Custom headers — Name	Content-Type
Custom headers — Prefix	(leave blank)
Custom headers — Value	application/json

Filled form — Name, Bearer type, allowed website, and custom header

Why Custom headers? The Nansen MCP server reads a NANSEN-API-KEY header directly — it does not use standard Bearer token authentication. Selecting Bearer as the credential type is what unlocks the Custom headers field.

After saving, navigate back to claude.ai/admin-settings/claude-tag and enable the access bundle. Under Access summary, Connections should show Nansen.

Done — version=New, bundle enabled, Nansen connection active in Access summary

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Step 3 — Invite Claude to a Slack channel

In any Slack channel where you want Nansen access, run:

/invite @Claude

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Step 4 — Verify

Tag Claude in the channel and ask a Nansen question:

@Claude what tokens are smart money buying on Ethereum today?

Claude will call the Nansen MCP server and return live data directly in Slack.

If Claude responds without data or says it can't access Nansen, double-check that the access bundle is enabled and that the NANSEN-API-KEY header value is correct.