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Version: v5

Harper MCP CLI

Added in: v5.1.0

harper mcp is a stdio bridge that lets MCP hosts (Claude Desktop, Cursor, Zed, or any client that speaks the stdio MCP transport) talk to a running Harper instance over Harper's Streamable HTTP MCP endpoint.

The CLI is bundled with Harper itself; if harper is on your PATH, so is harper mcp.

Subcommands​

harper mcp [subcommand] [flags]
SubcommandPurpose
(default)Run the stdio bridge — JSON-RPC frames on stdin, responses on stdout, until stdin closes.
print-configEmit a paste-ready config block for an MCP host (--client claude-desktop, cursor, or zed).
doctorConnect, complete an initialize handshake, list tools, clean up; report each step.
helpPrint the help text.

Connection modes​

harper mcp connects in one of two modes, chosen automatically based on whether --target is set:

Local UDS (default)​

With no --target flag, the CLI connects to the Harper running on the same host via the operations API Unix Domain Socket — the same socket bin/cliOperations uses. Filesystem permissions on the socket are the access gate; no credentials are required or sent.

The UDS path is derived from operationsApi.network.domainSocket in harperdb-config.yaml and is typically <rootPath>/sockets/operations-server.

Network HTTPS / HTTP​

--target https://node.example.com:9926 connects over the network to a remote Harper. Credentials are resolved with this precedence (highest first):

  1. --bearer <token> — explicit bearer token.
  2. --username + --password — explicit Basic auth.
  3. URL-embedded user/pass, e.g. --target https://alice:pw@node:9926.
  4. Saved JWT from ~/.harperdb/credentials.json for the resolved target (populated by harper login).

If none of these are present, the request goes out unauthenticated and Harper gates the response accordingly.

Use --insecure to skip TLS certificate validation (network mode only) — useful for local self-signed certs during development.

Flags​

FlagDefaultPurpose
--profile <name>applicationoperations or application. Determines which MCP endpoint the CLI connects to.
--target <url>(local UDS)Network endpoint. Switches the CLI into network mode.
--mount-path <path>/mcpOverrides the mount path. Match whatever mcp.<profile>.mountPath is set to.
--username <u>(none)Basic auth username (network mode).
--password <p>(none)Basic auth password (network mode).
--bearer <token>(none)Bearer token (network mode). Wins over --username / --password.
--insecure(off)Skip TLS certificate validation (network mode only).
--client <name>(required for print-config)claude-desktop, cursor, or zed.
--help, -h(off)Print the help text and exit.

harper mcp (the bridge)​

The default subcommand runs until stdin closes. The expected use is to invoke it from an MCP host's configuration block (see print-config below). Each line of stdin is parsed as a JSON-RPC frame and POSTed to the Harper MCP endpoint; each response (whether JSON or SSE-streamed) is emitted to stdout as line-delimited JSON-RPC.

After the initialize handshake completes, the bridge opens a long-lived GET /mcp request — Harper's server-push channel — and forwards every notifications/tools/list_changed and notifications/resources/list_changed frame to stdout. The host sees one unified MCP stream.

Logs (status, errors, dropped invalid stdin lines) go to stderr so they never collide with the JSON-RPC channel.

harper mcp print-config​

Emits a paste-ready JSON block for the requested MCP host along with a comment indicating where to put it.

harper mcp print-config --client claude-desktop

Produces:

# Target file: ~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or %APPDATA%\Claude\claude_desktop_config.json (Windows)
{
  "mcpServers": {
    "harper": {
      "command": "harper",
      "args": ["mcp"]
    }
  }
}
# Note: Restart Claude Desktop after editing the file.
# Note: Merge into an existing `mcpServers` block if you already have one.

The generated args array reflects whatever flags you pass to print-config (other than --client). For instance:

harper mcp print-config --client cursor --target https://node.example.com:9926 --profile operations

emits a block whose args is ["mcp", "--profile", "operations", "--target", "https://node.example.com:9926"]. This lets you generate fully-resolved config blocks for non-default deployments without hand-editing.

Supported clients:

  • claude-desktop — Anthropic Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json on macOS, %APPDATA%\Claude\claude_desktop_config.json on Windows).
  • cursor — Cursor IDE (~/.cursor/mcp.json).
  • zed — Zed editor (Zed settings.json, under context_servers).

harper mcp doctor​

Runs a three-step smoke check against the configured connection:

  1. POST initialize — verifies the transport works and Harper accepts the handshake. Captures the negotiated protocol version and session id.
  2. POST tools/list — verifies the session is usable and reports how many tools are visible to the authenticated user.
  3. DELETE /mcp — cleans up the session. This step is allowed to fail (when mcp.session.allowClientDelete is false the server returns 405); overall doctor exit is still success.

Each step prints [OK] or [FAIL] with a short detail line. Exit code is 0 on success, 1 on any non-tolerable failure.

$ harper mcp doctor --target https://node.example.com:9926 --bearer $TOKEN
[OK  ] initialize - session=ab12... protocol=2025-06-18
[OK  ] tools/list - 14 tool(s) visible
[OK  ] session cleanup

All checks passed.

Use doctor as a quick "is the wire path healthy?" check before pointing a real MCP host at the server.