A physics MCP server that shows its working: 31 calculators, 34 CODATA constants, no key

UsePhysics has listed a free, keyless remote MCP server, com.usephysics/physics-calculators, in the official MCP Registry, exposing 31 physics calculators across seven categories and 34 CODATA 2022 constants in six groups. The server offers four read-only tools — list_calculators, calculate, get_constant and list_constants — with calculate returning results in units, the formula, worked steps where derivable, and a link that reopens the solved calculator with inputs filled in. Constants come from NIST's 2022 CODATA listing, with exact values flagged as such.

If you are building a homework helper or a tutoring agent, the hard part of a physics question is rarely the arithmetic. It is the formula, the units and the steps a student can follow. Language models are good at explaining and still slip on numbers, so we gave our physics calculators a door that agents can call directly. Since yesterday 3 November 2026 the UsePhysics https://usephysics.com/?utm source=devto&utm medium=post&utm campaign=up-mcp-show-work-devto MCP server is listed in the official MCP Registry as com.usephysics/physics-calculators . It is a remote server Streamable HTTP , free, and it needs no key: https://usephysics.com/api/mcp Four read-only tools: | tool | what it returns | |---|---| | list calculators | every calculator: id, formula, input keys with units and defaults, page URL | | calculate | the results with units, the formula, the worked steps where the engine can derive them, and a link to the solved page | | get constant | one CODATA 2022 constant as NIST prints it, with its uncertainty or "exact" and the NIST source | | list constants | the constants we keep, in groups | As served today: 31 calculators in seven categories 15 of them mechanics: free fall, projectile motion, torque, tension, terminal velocity and so on and 34 constants in six groups, from the seven SI defining constants to particle masses. No SDK needed. This is plain Python against the live endpoint, and the output below is what it printed this morning: python import json, urllib.request URL = "https://usephysics.com/api/mcp" def call tool, args : body = {"jsonrpc": "2.0", "id": 1, "method": "tools/call", "params": {"name": tool, "arguments": args}} req = urllib.request.Request URL, json.dumps body .encode , { "Content-Type": "application/json", "Accept": "application/json, text/event-stream"} raw = urllib.request.urlopen req .read .decode data = next l 6: for l in raw.splitlines if l.startswith "data: " return json.loads json.loads data "result" "content" 0 "text" r = call "calculate", {"calculator id": "free-fall", "inputs": {"h": 20}} print i "key" + "=" + str i "value" for i in r "inputs" print "\n".join r "show work" print call "get constant", {"query": "planck constant"} "value as printed" 'h=20' Given: h = 20 m Formula: t = √ 2h/g Substitute: t = √ 2 × 20 / 9.80665 Result: t = 2.02 s 6.626 070 15 × 10^-34 The same answer also carries the impact speed 19.81 m/s, or 71.3 km/h and a link that reopens the solved calculator with the inputs filled in: usephysics.com/calculators/free-fall?h=20 https://usephysics.com/calculators/free-fall?h=20&utm source=devto&utm medium=post&utm campaign=up-mcp-show-work-devto . That link is the useful bit for a tutoring agent: the student gets a page they can change and re-run, not just a number in a chat. list calculators first and use its keys. h , kinetic energy takes m and v . Inputs are in the units listed next to each key. inputs array. show work: null . The formula is always there, so an agent can still explain the step itself. Constants come straight from NIST's 2022 CODATA listing retrieved 26 July 2026 , and exact constants say so: Planck's constant comes back with "exact": true and no uncertainty, because since 2019 it defines the kilogram. The answers are educational calculations from the formula shown. They are good for homework and for checking your own working, not for engineering sign-off. The full calculator list, with formulas, is also in usephysics.com/llms.txt https://usephysics.com/llms.txt .