Installing BlockRun MCP

One command per client, then one tool call to see the wallet. Do it in this order; the PATH step is the one people skip and then spend an hour on.

1. Check Node first

node -v      # must print v20.19 or newer
which npx

If node is from nvm, Homebrew, fnm, volta or asdf, assume the client's launcher will NOT find it. GUI-launched apps and Claude Code's MCP spawner do not source your shell profile. The fix is to pass your shell's PATH through at install time — not to pin nvm alias default, not to edit .zshrc, not to symlink node into /usr/local/bin.

2. Install — pick the client

Claude Code (recommended; -s user = every project):

claude mcp add blockrun -s user -e PATH="$PATH" -- npx -y @blockrun/mcp@latest

The -- matters: it stops -y being parsed by claude mcp add. The -e PATH="$PATH" is the nvm/Homebrew fix from step 1; it is harmless on a system Node, so always include it.

Codex CLI (--env is Codex's equivalent of -e; config lands in ~/.codex/config.toml):

codex mcp add blockrun --env PATH="$PATH" -- npx -y @blockrun/mcp@latest

Claude Desktop / Cursor / Windsurf — JSON, in the client's MCP config file:

{ "mcpServers": { "blockrun": { "command": "npx", "args": ["-y", "@blockrun/mcp@latest"] } } }

Client	File
Claude Desktop	claude_desktop_config.json (Settings → Developer → Edit Config)
Cursor	~/.cursor/mcp.json · Windows %APPDATA%\Cursor\mcp.json
Windsurf	~/.codeium/windsurf/mcp_config.json · Linux ~/.config/.codeium/windsurf/mcp_config.json

For a JSON client with nvm/Homebrew Node, put the absolute npx path (which npx) in command — there is no -e PATH equivalent there.

Optional flags (append after @latest): --profile trading|research|media|chat exposes a smaller tool set so the client loads fewer schemas. Omit for all 20 tools.

Optional env (-e KEY=value on Claude Code, "env": {} in JSON): BLOCKRUN_CONFIRM_SPEND=on asks before each paid call on clients that support MCP elicitation; BLOCKRUN_CONFIRM_THRESHOLD=0.05 limits that to calls above $0.05; BLOCKRUN_BUDGET_LIMIT=5 hard-caps the process at $5.

3. Restart, then prove it

Restart the client — for Claude Code that means quit and relaunch claude; a running session does not pick up a new server. Then:

claude mcp list        # expect:  blockrun: npx -y @blockrun/mcp@latest - ✓ Connected
claude mcp get blockrun  # confirms the scope and that PATH / any -e vars were captured

Inside the session, call blockrun_wallet with no arguments. It prints the wallet address, chain, and balance. That call is free and needs no funds — if it returns, the install works. Do not "test" with a paid tool.

4. The wallet and how paying works

• The server creates a wallet on first run: an EVM key in ~/.blockrun/.session (0600). On macOS/Linux it is also mirrored into the OS keychain, but the file stays authoritative unless the user opts into BLOCKRUN_KEYCHAIN=strict. Tell the user to back that file up — it is the only copy of the key; BlockRun cannot recover it.
• Payment is USDC per call over x402, on Base by default. There is no account, API key, or card. Free tools (blockrun_wallet, blockrun_models, blockrun_dex, crypto blockrun_price, blockrun_chat mode:"free") work with a $0 balance.
• To fund: blockrun_wallet action:"setup" shows the address and a QR. Send USDC on the Base network (Coinbase → Send → USDC → Base). $5 covers hundreds of data calls.
• Prefer Solana: blockrun_wallet action:"chain" chain:"solana" then action:"setup". Send USDC (SPL) on Solana. No restart. A few media/paid tools are Base-only and say so.

5. Optional: install the agent skills

The package ships 16 skills (which tool to use, worked examples, this one). Claude Code users: /plugin marketplace add BlockRunAI/blockrun-mcp. Everyone else:

npx -y @blockrun/mcp@latest skills install              # → ./.claude/skills
npx -y @blockrun/mcp@latest skills install --global     # → ~/.claude/skills
npx -y @blockrun/mcp@latest skills install --to ~/.codex/skills

Common mistakes

Mistake	Why it bites
Omitting -e PATH="$PATH" on nvm/Homebrew	spawn npx ENOENT / "Failed to connect" — the #1 support issue
Omitting -- before npx	-y is eaten by claude mcp add; npx then prompts and hangs
Testing with a paid tool	You cannot tell "unfunded" from "broken". Use blockrun_wallet.
Sending USDC on Ethereum mainnet	Wrong network; the Base address is the same string but the funds are elsewhere. Say "Base".
Funding inside a sandboxed client (Claude Desktop / Cowork / Web bash)	The wallet lives in the sandbox and dies with it. Test: if ~/.blockrun/.session is gone in the next session, you are sandboxed — install on the user's real machine.

If the install is done and something still fails, switch to the blockrun-debug skill.