feat: add some useful skills

skills/mcp-cli/SKILL.md

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+---
+name: mcp-cli
+description: Interface for MCP (Model Context Protocol) servers via CLI. Use when you need to interact with external tools, APIs, or data sources through MCP servers.
+---
+
+# MCP-CLI
+
+Access MCP servers through the command line. MCP enables interaction with external systems like GitHub, filesystems, databases, and APIs.
+
+## Commands
+
+| Command | Output |
+|---------|--------|
+| `mcp-cli` | List all servers and tools |
+| `mcp-cli info <server>` | Show server tools and parameters |
+| `mcp-cli info <server> <tool>` | Get tool JSON schema |
+| `mcp-cli grep "<pattern>"` | Search tools by name |
+| `mcp-cli call <server> <tool>` | Call tool (reads JSON from stdin if no args) |
+| `mcp-cli call <server> <tool> '<json>'` | Call tool with arguments |
+
+**Both formats work:** `<server> <tool>` or `<server>/<tool>`
+
+## Workflow
+
+1. **Discover**: `mcp-cli` → see available servers
+2. **Explore**: `mcp-cli info <server>` → see tools with parameters
+3. **Inspect**: `mcp-cli info <server> <tool>` → get full JSON schema
+4. **Execute**: `mcp-cli call <server> <tool> '<json>'` → run with arguments
+
+## Examples
+
+```bash
+# List all servers
+mcp-cli
+
+# With descriptions  
+mcp-cli -d
+
+# See server tools
+mcp-cli info filesystem
+
+# Get tool schema (both formats work)
+mcp-cli info filesystem read_file
+mcp-cli info filesystem/read_file
+
+# Call tool
+mcp-cli call filesystem read_file '{"path": "./README.md"}'
+
+# Pipe from stdin (no '-' needed!)
+cat args.json | mcp-cli call filesystem read_file
+
+# Search for tools
+mcp-cli grep "*file*"
+
+# Output is raw text (pipe-friendly)
+mcp-cli call filesystem read_file '{"path": "./file"}' | head -10
+```
+
+## Advanced Chaining
+
+```bash
+# Chain: search files → read first match
+mcp-cli call filesystem search_files '{"path": ".", "pattern": "*.md"}' \
+  | head -1 \
+  | xargs -I {} mcp-cli call filesystem read_file '{"path": "{}"}'
+
+# Loop: process multiple files
+mcp-cli call filesystem list_directory '{"path": "./src"}' \
+  | while read f; do mcp-cli call filesystem read_file "{\"path\": \"$f\"}"; done
+
+# Conditional: check before reading
+mcp-cli call filesystem list_directory '{"path": "."}' \
+  | grep -q "README" \
+  && mcp-cli call filesystem read_file '{"path": "./README.md"}'
+
+# Multi-server aggregation
+{
+  mcp-cli call github search_repositories '{"query": "mcp", "per_page": 3}'
+  mcp-cli call filesystem list_directory '{"path": "."}'
+}
+
+# Save to file
+mcp-cli call github get_file_contents '{"owner": "x", "repo": "y", "path": "z"}' > output.txt
+```
+
+**Note:** `call` outputs raw text content directly (no jq needed for text extraction)
+
+## Options
+
+| Flag | Purpose |
+|------|---------|
+| `-d` | Include descriptions |
+| `-c <path>` | Specify config file |
+
+## Common Errors
+
+| Wrong Command | Error | Fix |
+|---------------|-------|-----|
+| `mcp-cli server tool` | AMBIGUOUS_COMMAND | Use `call server tool` or `info server tool` |
+| `mcp-cli run server tool` | UNKNOWN_SUBCOMMAND | Use `call` instead of `run` |
+| `mcp-cli list` | UNKNOWN_SUBCOMMAND | Use `info` instead of `list` |
+| `mcp-cli call server` | MISSING_ARGUMENT | Add tool name |
+| `mcp-cli call server tool {bad}` | INVALID_JSON | Use valid JSON with quotes |
+
+## Exit Codes
+
+- `0`: Success
+- `1`: Client error (bad args, missing config)
+- `2`: Server error (tool failed)
+- `3`: Network error
+