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

Sign up at https://nexar.com
Create or join an organization
Access portal.nexar.com to create an application
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

Quit Claude Desktop completely
Start Claude Desktop again
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

Add the function to octopart_server.py
Decorate with @mcp.tool()
Update the catalog entry with the new tool name
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.

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

License

MIT License