atomic-context

Read-only MCP server for exact, citable values of fundamental physical constants, particle properties, and material properties — powered by Java Spring Boot + SQLite.

Why this exists

LLMs know physics. Their weights do not reliably reproduce the exact 12-decimal-place CODATA constants or the specific heat capacity of an obscure alloy at a non-standard temperature. atomic-context is a grounding layer: a deterministic, citable, offline knowledge server that any MCP-compatible client (Claude Desktop, Cursor, Continue.dev …) can call.

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Data sources (open-source only)

Dataset	Coverage	License	URL
NIST CODATA 2022 (SRD 121)	29 fundamental constants	U.S. Gov. Work (public domain)	https://physics.nist.gov/cuu/Constants/
PDG 2024	20 particles (leptons, baryons, bosons, quarks, mesons)	CC-BY-4.0	https://pdg.lbl.gov
NIST WebBook SRD 69	Thermophysical & mechanical properties	U.S. Gov. Work (public domain)	https://webbook.nist.gov
AFLOW (aflow.org)	Metals, alloys, intermetallics	CC-BY-4.0	http://aflow.org
OQMD	Metals, alloys, ceramics (DFT)	MIT	http://oqmd.org
Materials Project	Semiconductors, ceramics (DFT + exp)	CC-BY-4.0	https://materialsproject.org
NSM Semiconductor Archive	Semiconductors (exp.)	Free academic	https://www.ioffe.ru/SVA/NSM/Semicond/
refractiveindex.info	Optical (refractive index, absorption)	CC0	https://refractiveindex.info

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MCP Tools

Tool	Description
get_constant	Exact CODATA 2022 value for a physical constant by symbol or name
search_constants	Search constants by keyword or category
list_constant_categories	List all constant categories
get_particle	PDG 2024 properties (mass, spin, charge, lifetime) for a particle
search_particles	Search particles by name, symbol, or type
get_material_property	Specific property for a material at a given temperature
search_materials	Search materials by name, composition, or category
list_material_properties	All available properties for a material
get_material_properties_by_category	All properties of one category (mechanical/electrical/thermal/optical/magnetic)

Material categories

• metal — pure metals (Al, Cu, Fe, Ni, Ti, W, Au, Ag, Mg, Co, Mo, Cr)
• alloy — Al alloys (2024/6061/7075), Ti alloys (Ti-6Al-4V, Ti-6242), stainless steels (304, 316L, 17-4PH), carbon steels (1020, 4340), Ni superalloys (Inconel 625/718, Waspaloy, Haynes 230), Cu alloys (brass, bronze, BeCu), Co alloys (Stellite 6), refractory alloys (Mo-TZM), shape memory (NiTi)
• semiconductor — Si, Ge, GaAs, InP, GaN, 4H-SiC, 3C-SiC, GaP, InAs, CdTe, ZnO, Diamond
• ceramic — Al₂O₃, ZrO₂ (8YSZ), Si₃N₄, SiC, B₄C, TiB₂, MgO, BaTiO₃, HA, WC

Property categories

Category	Properties
mechanical	elastic_modulus, tensile_strength_ultimate, yield_strength, hardness_vickers, fracture_toughness, elongation_at_break
electrical	electrical_resistivity, carrier_mobility, bandgap, conductivity
thermal	thermal_conductivity, specific_heat_capacity, melting_point, thermal_expansion_coefficient, curie_temperature
optical	refractive_index, absorption_coefficient, optical_bandgap
magnetic	saturation_magnetization, coercivity, relative_permeability, curie_temperature

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Build & run

Requirements

• Java 21
• Maven 3.6+

Build

cd atomic-context
mvn clean package -DskipTests

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Transport modes

The server supports two transport modes, selected via a Spring profile. The @Tool methods are identical in both modes — only the transport layer changes.

stdio — Claude Desktop (local)

Communicates over stdin/stdout. Logging and banner output are disabled, and the web application type is forced to none to keep the stdio pipe clean.

java -jar target/atomic-context-1.0.0.jar --spring.profiles.active=stdio

Claude Desktop configuration

Add to ~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or %APPDATA%\Claude\claude_desktop_config.json (Windows):

{
  "mcpServers": {
    "atomic-context": {
      "command": "java",
      "args": [
        "-jar",
        "/absolute/path/to/atomic-context-1.0.0.jar",
        "--spring.profiles.active=stdio"
      ]
    }
  }
}

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SSE/HTTP — networked clients (default)

Exposes the MCP server over HTTP using Server-Sent Events. This is the default profile when no --spring.profiles.active flag is provided.

# Default (sse profile)
java -jar target/atomic-context-1.0.0.jar

# Explicit
java -jar target/atomic-context-1.0.0.jar --spring.profiles.active=sse

Endpoint	URL
SSE stream	http://localhost:8080/sse/atomic-context
MCP messages	http://localhost:8080/mcp/message

MCP client configuration

{
  "mcpServers": {
    "atomic-context": {
      "url": "http://localhost:8080/sse/atomic-context"
    }
  }
}

Production deployment

The port and SSE path can be overridden at runtime without any code changes:

java -jar atomic-context-1.0.0.jar \
  --spring.profiles.active=sse \
  --server.port=9090 \
  --spring.ai.mcp.server.sse-endpoint=/sse/atomic-context

Or via environment variables (Spring Boot maps them automatically):

export SERVER_PORT=9090
export SPRING_AI_MCP_SERVER_SSE_ENDPOINT=/sse/atomic-context
java -jar atomic-context-1.0.0.jar --spring.profiles.active=sse

For HTTPS in production, place a reverse proxy (Nginx, Caddy) in front and proxy to the local port. Critical Nginx settings for SSE:

location /sse/atomic-context {
    proxy_pass         http://127.0.0.1:8080/sse/atomic-context;
    proxy_http_version 1.1;
    proxy_set_header   Connection "";
    proxy_buffering    off;
    proxy_cache        off;
    proxy_read_timeout 24h;
}

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Configuration files

File	Purpose
application.properties	Shared config: MCP metadata, SQLite datasource, JPA, logging
application-sse.properties	SSE transport settings (port, endpoint path)
application-stdio.properties	stdio transport + full logging blackout

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Database location

The SQLite database is stored at ~/.atomic-context/atomic-context.db and is seeded automatically on first startup. The seed scripts in src/main/resources/db/seed/ are idempotent (INSERT OR IGNORE) and safe to re-run.

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License

MIT — data is attributed per-row to original open-source sources.