Sign up, get your API key, connect via MCP. Your AI agent gets 203 precision math methods — exact arithmetic, no floating point, no hallucination. Works with Claude, ChatGPT, Cursor, Windsurf, and any MCP client.
https://arithym.xyz/mcp as a remote MCP server. You'll be prompted to authorize with your email — no API key needed, no config files. OAuth handles everything automatically.
Pick a tier on the pricing page, enter your email, and accept the Terms of Service. You'll receive your API key — a string starting with mc_free_, mc_pro_, or mc_eng_.
Claude Desktop — Edit claude_desktop_config.json:
{
"mcpServers": {
"arithym": {
"url": "https://arithym.xyz/mcp",
"headers": {
"Authorization": "Bearer YOUR_API_KEY"
}
}
}
}
Replace YOUR_API_KEY with the key from Step 1. Restart Claude Desktop.
ChatGPT — Go to Settings → Connectors (or Apps) → Add custom connector:
# Server URL https://arithym.xyz/mcp # Authentication OAuth (automatic via authorize page)
Cursor / Windsurf / Other MCP clients — Add as a remote server:
# Server URL https://arithym.xyz/mcp # Transport SSE # Header Authorization: Bearer YOUR_API_KEY
https://arithym.xyz/mcp instead.
Once connected, your agent has 62 tools across 22 domains. Try these to confirm your connection works:
compute("12847", "93", "multiply")
factorize("48620")
fraction_math("0.1", "0.2", "add")
scratch_math([["multiply","99.95","1.0825"], ["multiply","$prev","3"]])
Arithym has 62 tools. You don't need to memorize them — your agent can call help() for a system overview, help("tool_name") for any tool's full guide, discover("keyword") to search all 203 methods, or recommend("describe your problem") to get the optimal tool suggestion.
Navigation — help, domain_check, discover, recommend, guide_call
Arithmetic — compute, factorize, fraction_math, exact_sqrt, rational_sqrt, exact_trig
Multi-step — scratch_math, scratch_math_units, slide
Workspace — field_create, field_add, field_read, field_derive, field_update, field_sensitivity_all, field_optimize
Compute graphs — graph_define, graph_forward, graph_sensitivity, graph_solve, graph_what_if, graph_learn
Calculus — graph_derivative, graph_gradient, graph_jacobian, graph_hessian, graph_taylor, graph_integral, graph_critical_points
Units — unit_factor, unit_check, list_units
22 domain modules via guide_call — arithmetic, fractions, roots, trig, matrix, statistics, calculus, chemistry, physics, finance, geometry, signals, complex, number theory, algebra, medical, materials, quantum, scientific, verification, units, sphere-spiral
Usage is tracked per API key. Both MCP and REST endpoints share the same daily counter.
Limits reset at midnight UTC. If you hit your limit, the server returns a 429 status. Upgrade anytime on the pricing page.
All requests require a Bearer token in the Authorization header. This is your API key from Step 1.
# HTTP header (set in your MCP client config)
Authorization: Bearer mc_free_aBcDeFgH...
Invalid or missing keys receive a 401 Unauthorized response. Deactivated keys receive 403. Rate-limited keys receive 429 with a Retry-After header.
Questions, bugs, or feature requests — email jacob@arithym.xyz.
For detailed tool documentation once connected, call help("tool_name") from your agent. Every tool has a built-in usage guide with examples, parameter descriptions, and routing advice.