MCLIP

MCP Command-Line Interface Profile — a CLI conformance profile over the Model Context Protocol.

If a service exposes an MCP server, any MCLIP-conformant client produces the same scriptable surface for it: the same command shape, the same flags, the same JSON envelope, the same exit codes.

MCP does not define a CLI itself. MCLIP defines a canonical CLI projection from MCP's protocol objects — a deterministic rendering layer that turns any MCP server into a uniform shell surface.

A tool's inputSchema becomes long flags. A tools/call result becomes a JSON envelope on stdout. An MCP error becomes a specific exit code.

Live site: https://mclip.dev

What this repo is

A standards-documentation project for MCLIP — a profile that defines how MCP-to-CLI client implementations expose MCP server capabilities as command-line invocations. MCLIP is not a new protocol and does not require vendor-side work; it is a client-side conformance layer that sits on top of MCP.

The MCP-to-CLI translation space already exists and is crowded (mcp2cli, MCPorter, MCPShim, f/mcptools, FastMCP generate-cli, Apify mcpc, IBM mcp-cli, developit/mcp-cmd). Each picks its own flag conventions, command shapes, output formats, error structures, and resource/prompt surfaces. A script written for one of them does not run against another. MCLIP standardises the translation itself.

Concretely — the same MCP tool, across wrappers:

# f/mcptools
mcp call create_issue --params '{"title":"Bug","body":"..."}' \
  npx -y @modelcontextprotocol/server-github

# Apify mcpc
mcpc @github tools-call create_issue title:="Bug" body:="..."

# Under MCLIP, every conformant wrapper:
<binary> github tools call create_issue --title "Bug" --body "..."

Different command verbs, different argument styles, different server references, different output shapes. MCLIP-Core (profile-v0.md §1.2, §2.5, §5) pins all four.

How MCP maps to the CLI

MCLIP doesn't try to turn every MCP message into a shell command. The projection draws three lines:

MCP element	MCLIP treatment
Tools, resources, prompts	User-facing commands. Tool input schemas project to long flags; results project to a JSON envelope on stdout. Resources expose list/read/templates/watch; prompts expose list/get.
Sampling, elicitation, roots	Runtime mechanics, not standalone commands. Surface as flags, interactive prompts (with non-interactive refusal per §14.12), or config — not invocations.
Initialize, transport, pagination, auth, progress, cancellation, diagnostics	CLI infrastructure: hidden handshake, --transport, --timeout, --cursor/--limit/--no-paginate, env-var credentials (§11), NDJSON progress on stderr (MCLIP-Streaming), SIGINT cancellation (§6.2), --verbose/--quiet.

MCP primitives become commands; MCP schemas become input contracts; MCP responses become a JSON envelope; MCP lifecycle and interaction mechanics become CLI runtime behaviour. The nine conformance modules in profile-v0.md §0.7 are organised around this split.

Specification set

Read in this order to orient:

#	File	What it covers
1	profile-v0.md	Normative profile specification — Core plus eight independently-claimable modules. Every rule tagged [MCLIP-§-NN] for conformance tracking.
2	security-model.md	Trust boundaries, destructive-action policy, CI-safe behaviour, credential handling, auditability.
3	conformance-fixtures.md	30+ executable conformance fixtures with expected exit codes and output shapes.
4	adoption-guide.md	For existing MCP-to-CLI wrapper maintainers — minimum surface for MCLIP-Core conformance and the per-module cost.
5	sep-standards-mclip-profile.md	Standards Track SEP draft (wraps the profile for filing under modelcontextprotocol/seps).
6	sep-extensions-mclip-metadata.md	Extensions Track SEP draft (optional mclip.* CLI-hint metadata keys, per SEP-2133).

Supporting docs:

• product-brief.md — one-pager summary.
• use-cases.md — concrete MCLIP use cases.
• real-mcp-servers.md — the prototype-validation real-server set.

Implementation specs:

• mclio-architecture.md — architecture spec for mclio, the production CLI that doubles as the standard's executable reference.
• fixtures-spec.md — implementation spec for the 9 synthetic MCP fixture servers.

Implementation

• fixtures/ — 9 synthetic MCP servers + verify harness, Go, pinned to github.com/modelcontextprotocol/go-sdk v1.6.0.
• mclio — production CLI (separate repo, in development). Greenfield Go binary; doubles as the standard's executable reference and the recommended daily-driver MCP CLI.
• site/ — Astro source for https://mclip.dev.

Canonical identity

• Public front door: https://mclip.dev
• Schema namespace: https://mclip.dev/schemas/config/v0.json (Draft 2020-12 JSON Schema; tracks profile-v0.md §13.3)
• Source repository: this repo (specs, fixtures, decisions).

Status

Pre-SEP. The core specification set is drafted and self-consistent. The 9 fixture servers and the verify harness are built. The remaining build queue is the mclio binary, the full conformance harness against it, and a companion consumer app.

Licence

Apache-2.0. See LICENSE.