feat: add global-chat-agent-discovery skill (#463)

* feat: add global-chat-agent-discovery skill for cross-protocol agent search

Adds a skill for discovering MCP servers and AI agents across 18K+ entries
and 6+ registries using Global Chat's directory and MCP server
(@global-chat/mcp-server). Covers MCP, A2A, and agents.txt protocols.

* docs: add README credit for global chat

---------

Co-authored-by: pumanitro <pumanitro@gmail.com>
Co-authored-by: sickn33 <sickn33@users.noreply.github.com>

README.md

@@ -284,6 +284,7 @@ This collection would not be possible without the incredible work of the Claude
 
 ### Community Contributors
 
+- **[pumanitro/global-chat](https://github.com/pumanitro/global-chat)**: Source for the Global Chat Agent Discovery skill - cross-protocol discovery of MCP servers and AI agents across multiple registries.
 - **[milkomida77/guardian-agent-prompts](https://github.com/milkomida77/guardian-agent-prompts)**: Source for the Multi-Agent Task Orchestrator skill - production-tested delegation patterns, anti-duplication, and quality gates for coordinated agent work.
 - **[Elkidogz/technical-change-skill](https://github.com/Elkidogz/technical-change-skill)**: Source for the Technical Change Tracker skill - structured JSON change records, session handoff, and accessible HTML dashboards for coding continuity.
 - **[rmyndharis/antigravity-skills](https://github.com/rmyndharis/antigravity-skills)**: For the massive contribution of 300+ Enterprise skills and the catalog generation logic.

skills/global-chat-agent-discovery/SKILL.md

@@ -0,0 +1,119 @@
+---
+name: global-chat-agent-discovery
+description: "Discover and search 18K+ MCP servers and AI agents across 6+ registries using Global Chat's cross-protocol directory and MCP server."
+category: development
+risk: safe
+source: community
+source_repo: pumanitro/global-chat
+source_type: community
+date_added: "2026-04-06"
+author: pumanitro
+tags: [mcp, ai-agents, agent-discovery, agents-txt, a2a, developer-tools]
+tools: [claude, cursor, gemini, codex]
+---
+
+# Global Chat Agent Discovery
+
+## Overview
+
+Global Chat is a cross-protocol AI agent discovery platform that aggregates MCP servers and AI agents from 6+ registries into a single searchable directory. This skill helps you find the right MCP server, A2A agent, or agents.txt endpoint for any task by searching across 18,000+ indexed entries. It also provides an MCP server (`@global-chat/mcp-server`) for programmatic access to the directory from any MCP-compatible client.
+
+## When to Use This Skill
+
+- Use when you need to find an MCP server for a specific capability (e.g., database access, file conversion, API integration)
+- Use when evaluating which agent registries carry tools for your use case
+- Use when you want to search across multiple protocols (MCP, A2A, agents.txt) simultaneously
+- Use when setting up agent-to-agent communication and need to discover available endpoints
+
+## How It Works
+
+### Option 1: Use the MCP Server (Recommended for Agents)
+
+Install the Global Chat MCP server to search the directory programmatically from Claude Code, Cursor, or any MCP client.
+
+```bash
+npm install -g @global-chat/mcp-server
+```
+
+Add to your MCP client configuration:
+
+```json
+{
+  "mcpServers": {
+    "global-chat": {
+      "command": "npx",
+      "args": ["-y", "@global-chat/mcp-server"]
+    }
+  }
+}
+```
+
+Then ask your agent to search for tools:
+
+```
+Search Global Chat for MCP servers that handle PostgreSQL database queries.
+```
+
+### Option 2: Use the Web Directory
+
+Browse the full directory at [https://global-chat.io](https://global-chat.io):
+
+1. Visit the search page and enter your query
+2. Filter by protocol (MCP, A2A, agents.txt)
+3. Filter by registry source
+4. View server details, capabilities, and installation instructions
+
+### Option 3: Validate Your agents.txt
+
+If you maintain an `agents.txt` file, use the free validator:
+
+1. Go to [https://global-chat.io/validate](https://global-chat.io/validate)
+2. Enter your domain or paste your agents.txt content
+3. Get instant feedback on format compliance and discoverability
+
+## Examples
+
+### Example 1: Find MCP Servers for a Task
+
+```
+You: "Find MCP servers that can convert PDF files to text"
+Agent (via Global Chat MCP): Searching across 6 registries...
+  - @anthropic/pdf-tools (mcpservers.org) — PDF parsing and text extraction
+  - pdf-converter-mcp (mcp.so) — Convert PDF to text, markdown, or HTML
+  - ...
+```
+
+### Example 2: Discover A2A Agents
+
+```
+You: "What A2A agents are available for code review?"
+Agent (via Global Chat MCP): Found 12 A2A agents for code review across 3 registries...
+```
+
+### Example 3: Check Agent Protocol Coverage
+
+```
+You: "How many registries list tools for Kubernetes management?"
+Agent (via Global Chat MCP): 4 registries carry Kubernetes-related agents (23 total entries)...
+```
+
+## Best Practices
+
+- Use the MCP server for automated workflows and agent-to-agent discovery
+- Use the web directory for manual exploration and comparison
+- Validate your agents.txt before publishing to ensure maximum discoverability
+- Check multiple registries — coverage varies significantly by domain
+
+## Common Pitfalls
+
+- **Problem:** Search returns too many results
+  **Solution:** Add protocol or registry filters to narrow the scope
+
+- **Problem:** MCP server not connecting
+  **Solution:** Ensure `npx` is available and run `npx -y @global-chat/mcp-server` manually first to verify
+
+## Related Skills
+
+- `@mcp-client` - For general MCP client setup and configuration
+- `@agent-orchestration-multi-agent-optimize` - For orchestrating multiple discovered agents
+- `@agent-memory-mcp` - For persisting discovered agent information across sessions