costheta — Claude Code MCP server: randomness from cosmic rays
Hooks your agent up to a remote source of verifiable physical randomness: a free beacon plus paid signed decisions.
claude mcp add --transport http costheta https://costheta.dev/mcpWhat costheta does
costheta is a remote MCP server that hands your agent values derived from cosmic-ray detections. The beacon tier is free; signed decisions are paid. It lives at https://costheta.dev/mcp, so nothing runs on your machine.
A public verifier, costheta-verify, checks the canonical hash of a certificate body along with its Ed25519 (RFC 8032) and ML-DSA (FIPS 204) signatures, comparing them against the public keys at costheta.dev/keys. Certificate format v0.3 is laid out in the federation proposal. The verifier code has not been published yet.
If you need randomness you can show to a third party, this is worth a look. For shuffling fixtures in a test suite, plain Math.random() does the job and costs nothing.
What it helps with
- get random values that can be checked against a published key
- sign an agent decision with Ed25519
- match a certificate body hash to a public key
- add a physical randomness source to an agent with no local dependencies
- verify an ML-DSA signature per FIPS 204
Example prompts for the agent
- Pull a random beacon value from costheta
- Verify this decision certificate against the keys at costheta.dev/keys
- Request a signed decision from costheta
How to install costheta
Platform CLI: remote server
claude mcp add --transport http costheta https://costheta.dev/mcpPlatform CLI: remote server
codex mcp add costheta --url https://costheta.dev/mcpConfig file
{
"mcpServers": {
"costheta": {
"url": "https://costheta.dev/mcp"
}
}
}Config file
{
"servers": {
"costheta": {
"type": "http",
"url": "https://costheta.dev/mcp"
}
}
}Platform CLI: remote server
gemini mcp add -t http costheta https://costheta.dev/mcpStep by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about costheta
How do I install costheta in Claude Code?
Run claude mcp add --transport http costheta https://costheta.dev/mcp. The server connects over HTTP, and there is no separate install step.
What does costheta do?
It supplies your agent with random values drawn from cosmic-ray detections. The free beacon works out of the box, while signed decisions are a paid tier.
What verifies costheta certificates?
The public costheta-verify tool: it checks the canonical body hash, the Ed25519 signature and the ML-DSA signature against the keys at costheta.dev/keys.
