Before the next tool call, find the crux
Give your agent the decisions your people already made
A hosted MCP server and HTTP API that return the questions whose answers would change what an agent does, and remember the answers, so the agent stops asking twice.
Quickstart2 steps
1. Register the server in Claude Code
claude mcp add --transport http cruxes \
"https://www.cruxes.io/api/mcp" \
--header "Authorization: Bearer $CRUXES_API_KEY"2. List the tools. This call is free
curl -s https://www.cruxes.io/api/mcp \
-H "Authorization: Bearer $CRUXES_API_KEY" \
-H "Content-Type: application/json" \
-H "Accept: application/json, text/event-stream" \
-d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'- Protocol
- MCP 2025-03-26, Streamable HTTP
- Sign-in
- API key or OAuth
- Read tools
- Free
- Stage
- Early access
Surfaces
Where you can connect
The state is the state today. Available means a person can use it now. Preview works but is not open to everyone. Planned is not released.
| Surface | What it does | Reach it at | State |
|---|---|---|---|
| Hosted MCP server | Read decisions, resolve a crux, find new ones, gate an action. Streamable HTTP, JSON-RPC. | https://www.cruxes.io/api/mcp | Available |
| API keys | Per-user keys (cxk_) with read, resolve and detect scopes, shown once, revocable. | /account/api-keys | Available |
| Claude.ai connector | Add Cruxes as a remote connector and sign in with OAuth. No key to paste. | https://www.cruxes.io/api/mcp | Available |
| Claude Code plugin | Reads what a person already decided so the agent does not ask again; slash commands call the exact tool. | Share and export, then Continue in Claude Code | Available |
| Agent trial | One tool, gate_cruxes, with no account, a few calls a day per address and nothing saved. | https://www.cruxes.io/api/trial/mcp | Available |
| Chrome extension | Surfaces cruxes in the page you are reading, connected to your account with its own token. | /extension/connect | Preview |
| Perplexity and Google Workspace | A connector for Perplexity, and a card view in Docs, Sheets and Slides. | See the release log | Preview |
| Slack app | Run /crux and resolve cruxes from a channel. | Not yet released | Planned |
Reference
The tools, and what each one costs
Every tool says whether it reads or writes and whether it is billed, so an agent's spend is never a surprise. The full list, with samples in curl, TypeScript and Python, is in the guide.
| Tool | What it does | Access | Cost |
|---|---|---|---|
get_handoff | Returns the cruxes you decided, each with the option you chose, any still open, and the plan. The place to start when continuing your work. | Reads | Free |
list_sessions | Lists your Cruxes web sessions, newest first, with title, goal and how many cruxes are decided and open. Can filter by a word in the title or goal. | Reads | Free |
get_session | Returns one session in full: the recent conversation, every crux with your decision, open questions and the plan. | Reads | Free |
list_cruxes | Lists cruxes (questions whose answers change what to do) with headline, deadline and status. Open ones by default; can show decided ones or all. | Reads | Free |
get_crux | Returns one crux in full: the question, options with probabilities and expected value, evidence, assumptions and the recommended action. | Reads | Free |
resolve_crux | Records the option you choose for an open crux. The host is told to call it only after you say which option you choose. | Writes | Free |
detect_cruxes | Finds the cruxes in a plan or answer you give it, and saves them to a new session in your account so you can answer them. It decides nothing. Takes up to about 15 seconds, longer at walkthrough depth. | Writes | Metered: each crux returned counts against your plan's allowance, the same as in the web app |
Clients
Use Cruxes in your agent
The same hosted server works from any MCP client. Each client gets a page with setup, a test case and sample code as it is tested.
Claude Code
Set it up, run a test case, and read the sample code. The written walk-through is in the blog.
Demo comingCodex
Set it up, run a test case, and read the sample code.
Demo comingCursor
Set it up, run a test case, and read the sample code.
Demo comingGrok
Set it up, run a test case, and read the sample code.
Demo coming
Latest
What changed, and what we wrote
Credentials
Get a key in three steps
- Sign in. Keys belong to your account. You come back to this page afterwards.
- Create a key. Name it, choose what it may do (read, resolve, detect) and set when it expires. It is shown once.
- Test it. One button lists the tools the key can see before you paste it into an agent.
Cruxes is in early access. Sign in to get 15 free Cruxes.
Ask a question, or tell us what is missing
The community is not open yet. It will be an invite-only Discord with rooms for the MCP and agents, and forums for bugs and requests. Until then, contact us from the Company page.