feat: add Composio as integration layer for OAuth-heavy marketing tools

Adds Composio MCP server as an alternative integration method for tools
lacking native MCP support (HubSpot, Salesforce, Meta Ads, LinkedIn Ads,
Google Sheets, Slack, Notion, etc.). Existing CLIs and MCP servers are
unchanged — Composio is additive only.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

AGENTS.md

@@ -22,6 +22,7 @@ marketingskills/
 │       └── SKILL.md       # Required skill file
 ├── tools/
 │   ├── clis/              # Zero-dependency Node.js CLI tools (51 tools)
+│   ├── composio/          # Composio integration layer (quick start + toolkit mapping)
 │   ├── integrations/      # API integration guides per tool
 │   └── REGISTRY.md        # Tool index with capabilities
 ├── CONTRIBUTING.md
@@ -167,7 +168,8 @@ This repository includes a tools registry for agent-compatible marketing tools.
 
 - **Tool discovery**: Read `tools/REGISTRY.md` to see available tools and their capabilities
 - **Integration details**: See `tools/integrations/{tool}.md` for API endpoints, auth, and common operations
-- **MCP-enabled tools**: ga4, stripe, mailchimp, google-ads, resend, zapier, zoominfo, clay, supermetrics, coupler, outreach, crossbeam
+- **MCP-enabled tools**: ga4, stripe, mailchimp, google-ads, resend, zapier, zoominfo, clay, supermetrics, coupler, outreach, crossbeam, composio
+- **Composio** (integration layer): Adds MCP access to OAuth-heavy tools without native MCP servers (HubSpot, Salesforce, Meta Ads, LinkedIn Ads, Google Sheets, Slack, etc.). See `tools/integrations/composio.md`
 
 ### Registry Structure
 
@@ -189,6 +191,8 @@ Skills reference relevant tools for implementation. For example:
 - `email-sequence` skill → customer-io, mailchimp, resend guides
 - `paid-ads` skill → google-ads, meta-ads, linkedin-ads guides
 
+For tools without native MCP servers (HubSpot, Salesforce, Meta Ads, LinkedIn Ads, Google Sheets, Slack, Notion), Composio provides MCP access via a single server. See `tools/integrations/composio.md` for setup and `tools/composio/marketing-tools.md` for the full toolkit mapping.
+
 ## Checking for Updates
 
 When using any skill from this repository: