Nexar MCP Server

A Model Context Protocol (MCP) server for searching electronic components and retrieving datasheets via the Nexar API (formerly Octopart API).

Keywords: Nexar, Octopart, MCP, electronic components, part search, datasheet, BOM, component sourcing, electronics design, PCB, Claude, AI assistant

Purpose

This MCP server provides a secure interface for AI assistants to search the Octopart/Nexar component database, compare pricing across distributors, check availability, and retrieve datasheet URLs. Perfect for electronics engineers using Claude Desktop or other MCP-compatible AI assistants.

Features

Component-Specific Tools

The server exposes specialized tools for different component types, allowing the AI client to select the appropriate tool and pass structured parameters:

Tool	Description
find_resistors	Search resistors by resistance, tolerance, power rating, mounting (SMD/through-hole)
find_capacitors	Search capacitors by capacitance, voltage, dielectric, mounting (SMD/through-hole)
find_inductors	Search inductors by inductance, current rating, DCR, mounting (SMD/through-hole), shielded
find_semiconductors	Search MCUs, transistors, ICs, diodes by part number, mounting (SMD/through-hole)
find_crystals	Search crystals/oscillators by frequency, ppm tolerance, mounting (SMD/through-hole)
find_connectors	Search connectors by type, pin count, pitch, mounting
search_components	Generic fallback for part numbers or unknown component types
search_bom	Bulk search multiple components in one call (for BOMs)
get_part_details	Get full specs, pricing, and availability for a specific MPN
get_datasheet	Get datasheet URL for a specific MPN

Common Parameters

All search tools share these parameters:

Parameter	Type	Description
manufacturer	string	Filter by manufacturer name
max_price	float	Maximum unit price in USD
distributor	string	Filter to specific distributor (digikey, mouser, etc.)
quantity	int	Quantity for price break lookup and sorting
in_stock_only	bool	Only show parts with stock
limit	int	Max results to return (default: 10)

Usage Examples

Just ask Claude naturally - it will select the appropriate tool automatically.

Resistors

• "Find me a 10k 1% resistor in 0805 package"
• "I need 100 qty of 4.7k 0.25W resistors from DigiKey"
• "Search for 100 ohm 5% 0402 resistors under $0.01"

Capacitors

• "Find a 100nF 16V X7R capacitor in 0805"
• "I need 10uF 25V caps in 1206 from Mouser"
• "Search for 47pF C0G capacitors in 0402 package"

Inductors

• "Find a 2.2uH SMD inductor"
• "Find a 10uH inductor rated for 2A, shielded"
• "I need a 100nH 0603 inductor from DigiKey"
• "Search for 4.7uH through-hole inductors with 3A current rating"

Semiconductors

• "Find STM32F103C8T6"
• "I need an N-channel MOSFET rated for 60V 10A in SO-8"
• "Search for ESP32-WROOM modules in stock"
• "Find LM7805 voltage regulators at DigiKey, I need 25"

Crystals

• "Find an 8MHz crystal with 20ppm tolerance in HC-49 package"
• "I need a 32.768kHz crystal with 12pF load capacitance"
• "Search for 25MHz crystals with 10ppm or better"

Connectors

• "Find USB-C receptacles for SMD mounting"
• "I need a 4-pin JST-PH connector with 2mm pitch"
• "Search for RJ45 jacks"
• "Find 40-pin male headers with 2.54mm pitch"

Part Number Lookup

• "Look up part number LM358"
• "Find ATmega328P-PU in stock"
• "Search for BME280 sensors at Mouser"

Part Details and Datasheets

• "Get me the datasheet for STM32F103C8T6"
• "Show me full details and pricing for RC0805JR-0710KL"

Distributor Filtering

You can filter results to specific distributors:

• DigiKey
• Mouser
• Newark
• Arrow
• Farnell
• LCSC

Example: "Find 10k resistors in stock at DigiKey with at least 100 quantity"

BOM Search (Bulk Component Lookup)

Search multiple components in a single call using search_bom. Pass a JSON object with arrays for each component type:

{
  "resistors": [
    {"resistance": "10k", "tolerance": "1%", "package": "0805"},
    {"resistance": "4.7k", "package": "0603"}
  ],
  "capacitors": [
    {"capacitance": "100nF", "voltage_rating": "16V", "dielectric": "X7R", "package": "0805"},
    {"capacitance": "10uF", "voltage_rating": "25V"}
  ],
  "semiconductors": [
    {"query": "STM32F103C8T6"}
  ]
}

Supported component arrays:

• resistors - same parameters as find_resistors
• capacitors - same parameters as find_capacitors
• inductors - same parameters as find_inductors
• semiconductors - same parameters as find_semiconductors
• crystals - same parameters as find_crystals
• connectors - same parameters as find_connectors
• components - same parameters as search_components (generic fallback)

Parameters:

• bom_json (string): JSON object with component arrays
• default_limit (int): Results per component (default: 1). Override per-component with "limit" field.

Example: "Search for these BOM components: 10k 1% 0805 resistor, 100nF X7R capacitor, and STM32F103"

Query Best Practices

Based on extensive testing against the Nexar API, here are tips for optimal results:

Include Package in Query String (Recommended)

For semiconductors and complex components, include package specs directly in the query parameter rather than using the separate package filter:

# Better results - package in query
find_semiconductors(query="N-channel MOSFET 60V SO-8")
find_semiconductors(query="2N2222 NPN SOT-23")

# May return fewer results - package as separate filter
find_semiconductors(query="N-channel MOSFET 60V", package="SO-8")

Keep Queries Focused

Simpler queries with key specifications often return better results than overly detailed queries:

# Good - focused query
find_semiconductors(query="STM32 microcontroller", distributor="digikey")

# May return 0 results - too specific
find_semiconductors(query="STM32 32-bit 3.3V microcontroller 20 GPIO")

Use Filters for Business Constraints

The distributor, quantity, max_price, and in_stock_only filters work reliably:

find_resistors(resistance="10k", tolerance="1%", distributor="mouser", quantity=100)
find_capacitors(capacitance="100nF", max_price=0.05, in_stock_only=True)

Passive Components Work Well with Filters

For resistors, capacitors, inductors, and crystals, the dedicated parameters work reliably:

find_resistors(resistance="4.7k", tolerance="1%", package="0805")
find_capacitors(capacitance="10uF", voltage_rating="16V", dielectric="X5R")
find_inductors(inductance="10uH", current_rating="2A", shielded=True)
find_crystals(frequency="8MHz", ppm_tolerance="20ppm")

Prerequisites

• Docker Desktop with MCP Toolkit enabled
• Docker MCP CLI plugin (docker mcp command)
• Nexar API credentials (client ID and secret)

Getting Nexar API Credentials

1. Sign up at https://nexar.com
2. Create or join an organization
3. Access portal.nexar.com to create an application
4. Note your Client ID and Client Secret

Installation

Step 1: Build Docker Image

docker build -t nexar-mcp-server .

Step 2: Set Up Secrets

docker mcp secret set NEXAR_CLIENT_ID="your-client-id"
docker mcp secret set NEXAR_CLIENT_SECRET="your-client-secret"

# Verify secrets
docker mcp secret ls

Step 3: Create Custom Catalog

Create or edit ~/.docker/mcp/catalogs/custom.yaml:

version: 2
name: custom
displayName: Custom MCP Servers
registry:
  nexar:
    description: "Search electronic components and get datasheets via Nexar/Octopart API"
    title: "Nexar"
    type: server
    dateAdded: "2025-12-05T00:00:00Z"
    image: nexar-mcp-server:latest
    ref: ""
    readme: ""
    toolsUrl: ""
    source: ""
    upstream: ""
    icon: ""
    tools:
      - name: find_resistors
      - name: find_capacitors
      - name: find_inductors
      - name: find_semiconductors
      - name: find_crystals
      - name: find_connectors
      - name: search_components
      - name: get_datasheet
      - name: get_part_details
    secrets:
      - name: NEXAR_CLIENT_ID
        env: NEXAR_CLIENT_ID
        example: "your-client-id"
      - name: NEXAR_CLIENT_SECRET
        env: NEXAR_CLIENT_SECRET
        example: "your-client-secret"
    metadata:
      category: integration
      tags:
        - electronics
        - components
        - nexar
        - octopart
        - hardware
      license: MIT
      owner: local

Step 4: Update Registry

Edit ~/.docker/mcp/registry.yaml and add under the registry: key:

registry:
  # ... existing servers ...
  nexar:
    ref: ""

Step 5: Configure Claude Desktop

Find your Claude Desktop config file:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json
• Linux: ~/.config/Claude/claude_desktop_config.json

Ensure your custom catalog is included in the args array:

{
  "mcpServers": {
    "mcp-toolkit-gateway": {
      "command": "docker",
      "args": [
        "run",
        "-i",
        "--rm",
        "-v", "/var/run/docker.sock:/var/run/docker.sock",
        "-v", "/Users/YOUR_USERNAME/.docker/mcp:/mcp",
        "docker/mcp-gateway",
        "--catalog=/mcp/catalogs/docker-mcp.yaml",
        "--catalog=/mcp/catalogs/custom.yaml",
        "--config=/mcp/config.yaml",
        "--registry=/mcp/registry.yaml",
        "--tools-config=/mcp/tools.yaml",
        "--transport=stdio"
      ]
    }
  }
}

Step 6: Restart Claude Desktop

1. Quit Claude Desktop completely
2. Start Claude Desktop again
3. Your new tools should appear!

Configuration

The server supports optional configuration via environment variables. By default, results are sorted by lowest price at 100 quantity.

Available Settings

Variable	Default	Description
NEXAR_DEFAULT_SORT_QUANTITY	100	Quantity break used for price sorting (e.g., 100, 1000)
NEXAR_DEFAULT_DISTRIBUTOR	(none)	Always filter to this distributor (e.g., "digikey", "mouser")
NEXAR_DEFAULT_IN_STOCK_ONLY	false	Only show in-stock parts by default

Setting Configuration

Add environment variables to your catalog entry in ~/.docker/mcp/catalogs/custom.yaml:

registry:
  nexar:
    # ... other settings ...
    env:
      - name: NEXAR_DEFAULT_SORT_QUANTITY
        value: "100"
      - name: NEXAR_DEFAULT_DISTRIBUTOR
        value: "digikey"
      - name: NEXAR_DEFAULT_IN_STOCK_ONLY
        value: "true"

Or for local testing, set environment variables directly:

export NEXAR_DEFAULT_SORT_QUANTITY=1000
export NEXAR_DEFAULT_DISTRIBUTOR=mouser
export NEXAR_DEFAULT_IN_STOCK_ONLY=true

Architecture

Claude Desktop -> MCP Gateway -> Nexar MCP Server -> Nexar GraphQL API (Octopart)
                                       |
                              Docker Desktop Secrets
                              (NEXAR_CLIENT_ID,
                               NEXAR_CLIENT_SECRET)

Development

Local Testing

# Set environment variables for testing
export NEXAR_CLIENT_ID="your-client-id"
export NEXAR_CLIENT_SECRET="your-client-secret"

# Run directly
python octopart_server.py

# Test MCP protocol
echo '{"jsonrpc":"2.0","method":"tools/list","id":1}' | python octopart_server.py

Adding New Tools

1. Add the function to octopart_server.py
2. Decorate with @mcp.tool()
3. Update the catalog entry with the new tool name
4. Rebuild the Docker image

Troubleshooting

Tools Not Appearing

• Verify Docker image built successfully
• Check catalog and registry files
• Ensure Claude Desktop config includes custom catalog
• Restart Claude Desktop

Authentication Errors

• Verify secrets with docker mcp secret list
• Ensure secret names match in code and catalog
• Check that your Nexar application has the Supply scope enabled

No Results Found

• Try a broader search query
• Check that the part number is correct
• Some parts may not be in the Nexar/Octopart database

Security Considerations

• All secrets stored in Docker Desktop secrets
• Never hardcode credentials
• Running as non-root user
• Sensitive data never logged

API Rate Limits

The Nexar API has usage limits based on your subscription plan. Each search query counts against your monthly quota based on the number of matched parts returned.

Related

• Nexar API Documentation
• Octopart - The component search engine powered by Nexar
• Model Context Protocol - The protocol this server implements

License

MIT License