docs(mcp): add MCP module documentation

docs/mcp/README.md

@@ -0,0 +1,318 @@
+# PLEIADES MCP Server
+
+PLEIADES provides an optional MCP (Model Context Protocol) server that enables AI-assisted neutron resonance analysis. The MCP server exposes PLEIADES workflow functions as tools that AI applications (Claude Code, Claude Desktop, Cursor, etc.) can invoke.
+
+> **Note**: MCP support is available in PLEIADES v2.2.0+
+
+## What is MCP?
+
+[Model Context Protocol](https://modelcontextprotocol.io/) is an open standard for connecting AI applications to external systems. It provides a standardized way for AI models to access data sources, use tools, and execute workflows. Think of it as "USB-C for AI applications."
+
+## Installation
+
+### From PyPI
+
+```bash
+pip install pleiades-neutron[mcp]
+```
+
+### Editable Install (Development)
+
+```bash
+git clone https://github.com/lanl/PLEIADES.git
+cd PLEIADES
+pip install -e ".[mcp]"
+```
+
+### Using Pixi
+
+```bash
+pixi install -e mcp
+pixi run mcp-server
+```
+
+## Quick Start
+
+### 1. Start the MCP Server
+
+```bash
+# Using console script
+pleiades-mcp
+
+# Or using module invocation
+python -m pleiades.mcp
+```
+
+### 2. Register with Claude Code
+
+Create a `.mcp.json` file in your project directory:
+
+```json
+{
+  "mcpServers": {
+    "pleiades": {
+      "command": "pleiades-mcp"
+    }
+  }
+}
+```
+
+For Pixi-based projects:
+
+```json
+{
+  "mcpServers": {
+    "pleiades": {
+      "command": "pixi",
+      "args": ["run", "mcp-server"]
+    }
+  }
+}
+```
+
+### 3. Use with Claude Code
+
+Once registered, Claude Code will automatically connect to the PLEIADES MCP server. You can then make natural language requests:
+
+- "Validate the dataset at ./datasets/hafnium"
+- "Extract the manifest from this resonance data"
+- "Analyze the neutron resonance data using the Docker backend"
+
+## Workflow Overview
+
+The MCP tools orchestrate the following workflow:
+
+```mermaid
+flowchart TD
+    A[Validate Dataset] --> B[Extract Manifest]
+    B --> C{Detect Workflow Type}
+    C -->|raw + open_beam| D[Full Workflow]
+    C -->|sammy_data only| E[Simplified Workflow]
+    D --> F[Normalize Data]
+    F --> G[Run SAMMY]
+    E --> G
+    G --> H[Parse Results]
+    H --> I["chi², fit quality, isotope abundances"]
+```
+
+## Available Tools
+
+### `validate_resonance_dataset`
+
+Validate a neutron resonance dataset structure and check readiness for analysis.
+
+**Parameters:**
+| Name | Type | Required | Description |
+|------|------|----------|-------------|
+| `dataset_path` | string | Yes | Path to the dataset directory |
+
+**Returns:** Validation result with:
+- `valid`: Overall validity status
+- `can_run_full_workflow`: Whether full imaging workflow is available
+- `can_run_simplified_workflow`: Whether SAMMY-only workflow is available
+- `recommended_workflow`: `"full"`, `"simplified"`, or `None`
+- `issues`: List of validation issues with severity and messages
+
+### `extract_resonance_manifest`
+
+Extract and parse the manifest from a neutron resonance dataset.
+
+**Parameters:**
+| Name | Type | Required | Description |
+|------|------|----------|-------------|
+| `dataset_path` | string | Yes | Path to the dataset directory |
+
+**Manifest file search order:**
+1. `manifest_intermediate.md`
+2. `smcp_manifest.md`
+3. `manifest.md`
+
+**Returns:** Manifest data including:
+- `name`, `description`, `version`: Basic metadata
+- `facility`, `beamline`, `detector`: Experiment info
+- `isotope`: Primary isotope (e.g., "Hf-177")
+- `isotopes`: Explicit isotope list (takes priority over natural abundance)
+- `material_properties`: Density, atomic mass, temperature
+
+See [Manifest Format](manifest-format.md) for complete specification.
+
+### `analyze_resonance`
+
+Perform neutron resonance analysis on a dataset using SAMMY.
+
+**Parameters:**
+| Name | Type | Required | Default | Description |
+|------|------|----------|---------|-------------|
+| `dataset_path` | string | Yes | - | Path to the dataset directory |
+| `backend` | string | No | `"auto"` | SAMMY backend: `"auto"`, `"local"`, or `"docker"` |
+| `isotopes` | list[str] | No | `None` | Specific isotopes to analyze (e.g., `["Hf-177", "Hf-178"]`) |
+
+**Isotope Selection Priority:**
+
+When determining which isotopes to analyze, PLEIADES uses this priority order:
+
+1. **`isotopes` parameter** (highest priority) - If you pass isotopes to the function
+2. **Manifest `isotopes` field** - Explicit list in the manifest file
+3. **Manifest `enrichment` field** - Custom isotope composition (when `use_natural_abundance: false`)
+4. **Natural abundance lookup** (default) - Uses PLEIADES isotope database
+
+**Returns:** Analysis result with:
+- `success`: Whether analysis completed
+- `workflow_type`: `"simplified"` or `"full"`
+- `chi_squared`, `reduced_chi_squared`: Fit quality metrics
+- `fit_quality`: `"excellent"`, `"good"`, `"acceptable"`, or `"poor"`
+- `isotope_results`: Per-isotope abundances and uncertainties
+- `output_dir`, `lpt_file`, `lst_file`: Output file paths
+
+## Output Format
+
+All tools return JSON-serializable dictionaries with a consistent format:
+
+**Success:**
+```json
+{
+  "status": "success",
+  "data": {
+    "valid": true,
+    "recommended_workflow": "simplified",
+    ...
+  }
+}
+```
+
+**Error:**
+```json
+{
+  "status": "error",
+  "error": "Dataset validation failed: missing sammy_data/ directory"
+}
+```
+
+**Common error messages:**
+- `"No manifest found in /path (searched: manifest_intermediate.md, smcp_manifest.md, manifest.md)"`
+- `"Dataset validation failed: ..."`
+- `"SAMMY execution failed: ..."`
+- `"No SAMMY backend available"`
+- `"ENDF parameter file not found for isotope: Hf-999"`
+
+## Backend Options
+
+The `analyze_resonance` tool supports multiple SAMMY execution backends:
+
+| Backend | Description | Requirements |
+|---------|-------------|--------------|
+| `auto` | Auto-detect best available (tries Docker first, then local) | Any of the below |
+| `local` | Run SAMMY binary directly | SAMMY installed locally |
+| `docker` | Run SAMMY in Docker container | Docker installed and running |
+
+> **Note**: The `nova` backend (ORNL NOVA service) is currently disabled due to package instability.
+
+## Programmatic Usage
+
+You can also use the MCP tools directly in Python without the server:
+
+```python
+from pleiades.mcp.tools import (
+    validate_resonance_dataset,
+    extract_resonance_manifest,
+    analyze_resonance,
+)
+
+# Validate a dataset
+result = validate_resonance_dataset("/path/to/dataset")
+if result["status"] == "success":
+    data = result["data"]
+    print(f"Valid: {data['valid']}")
+    print(f"Recommended workflow: {data['recommended_workflow']}")
+    for issue in data.get("issues", []):
+        print(f"  [{issue['severity']}] {issue['message']}")
+else:
+    print(f"Validation error: {result['error']}")
+
+# Extract manifest
+manifest = extract_resonance_manifest("/path/to/dataset")
+if manifest["status"] == "success":
+    data = manifest["data"]
+    print(f"Isotope: {data['isotope']}")
+    print(f"Isotopes list: {data.get('isotopes')}")  # May be None
+
+# Run analysis
+analysis = analyze_resonance(
+    "/path/to/dataset",
+    backend="docker",
+    isotopes=["Hf-177", "Hf-178"]
+)
+if analysis["status"] == "success":
+    data = analysis["data"]
+    print(f"Success: {data['success']}")
+    print(f"Chi-squared: {data['chi_squared']}")
+    print(f"Fit quality: {data['fit_quality']}")
+    for iso_result in data.get("isotope_results", []):
+        print(f"  {iso_result['isotope']}: {iso_result['abundance']:.4f}")
+else:
+    print(f"Analysis error: {analysis['error']}")
+```
+
+## Checking MCP Availability
+
+```python
+from pleiades.mcp import MCP_AVAILABLE, check_mcp_available
+
+if MCP_AVAILABLE:
+    from pleiades.mcp.server import get_server
+    server = get_server()
+else:
+    print("MCP not installed. Run: pip install pleiades-neutron[mcp]")
+
+# Or raise ImportError with instructions
+check_mcp_available()  # Raises if not installed
+```
+
+## Security Notes
+
+> **WARNING**: MCP tools have file system access to any path the server process can read.
+
+- Path traversal (`../`) is **explicitly permitted** by design
+- An AI client can read any file accessible to the MCP server process user
+- **Never** run the MCP server as root or with elevated privileges
+- Consider OS-level sandboxing (Docker, chroot) in production environments
+- Use filesystem ACLs to restrict access to sensitive data directories
+
+## Troubleshooting
+
+### "No SAMMY backend available"
+
+No backend could be found. Solutions:
+1. **Docker**: Ensure Docker is running (`docker info`)
+2. **Local**: Install SAMMY and ensure it's in your PATH
+
+### "ENDF parameter file not found for isotope: X"
+
+The specified isotope doesn't have ENDF data available. Solutions:
+1. Check isotope format (e.g., `"Hf-177"` not `"177Hf"`)
+2. Verify the isotope exists in the ENDF library
+3. Use a different isotope that has available data
+
+### "Docker not running" or connection errors
+
+```bash
+# Check Docker status
+docker info
+
+# Start Docker if needed (Linux)
+sudo systemctl start docker
+
+# On macOS/Windows, start Docker Desktop
+```
+
+### MCP server not connecting
+
+1. Verify `.mcp.json` is in your project root
+2. Check the command path is correct
+3. Restart Claude Code after editing `.mcp.json`
+
+## Related Documentation
+
+- [Manifest Format Specification](manifest-format.md)
+- [Integration Pattern Guide](integration-pattern.md) - How to add MCP to other scientific packages
+- [MCP Protocol Specification](https://modelcontextprotocol.io/)