ZCP MCP Protocol Reference

This document describes the MCP-facing surface implemented by ZCP. Use it as a wire reference, not as the first conceptual introduction.

Lifecycle

Supported lifecycle methods:

initialize
initialized
ping

initialize returns MCP-shaped data including:

protocolVersion
serverInfo
capabilities

When auth metadata is configured on the native runtime, that information is also reflected through the exposed metadata surfaces.

Tools

Supported tool methods:

tools/list
tools/call
notifications/tools/list_changed

Supported tool metadata projection includes:

name
title
description
inputSchema
outputSchema
annotations
icons
execution
_meta

tools/call can return:

normal inline content
structured content
task objects when task-augmented invocation is requested and supported

Resources

Supported resource methods:

resources/list
resources/templates/list
resources/read
resources/subscribe
resources/unsubscribe
notifications/resources/updated
notifications/resources/list_changed

ZCP projects text-like, JSON-like, and binary handler outputs into MCP-compatible resource content.

Prompts

Supported prompt methods:

prompts/list
prompts/get
notifications/prompts/list_changed

Prompt results can be returned as:

plain string content
{role, content} messages
richer content block objects

Completion

Supported completion methods:

official completion/complete
compatibility alias completions/complete

Completion responses include:

values
total
hasMore

Logging

Supported logging methods and notifications:

logging/setLevel
notifications/message

Supported levels:

debug
info
notice
warning
error
critical
alert
emergency

Roots

Supported roots methods and notifications:

roots/list
notifications/roots/list_changed

Progress

Supported progress notification:

notifications/progress

Progress tokens are accepted from common MCP metadata locations, including:

params.meta.progressToken
params.meta.progress_token
params._meta.progressToken

Sampling

Supported method:

sampling/createMessage

Supported normalized request fields include:

messages
systemPrompt
modelPreferences
includeContext
temperature
maxTokens
stopSequences
metadata
tools
toolChoice

Elicitation

Supported elicitation methods:

official elicitation/create
compatibility alias elicitation/request

ZCP accepts MCP-style form and URL requests while still preserving a backward compatible alias path for native callers that have not migrated.

Tasks

Supported task methods:

tasks/create
tasks/list
tasks/get
tasks/result
tasks/cancel
notifications/tasks/status

Supported task states include:

queued
working
input_required
completed
failed
cancelled

Task-augmented tools/call is also supported for tools that declare task support.

Transports

Current MCP-facing transports:

stdio
streamable HTTP on /mcp
websocket on /ws

Current native transport:

JSON-RPC on /zcp

Streamable HTTP Details

/mcp supports:

GET for SSE streaming
POST for JSON-RPC and streamed responses
DELETE for explicit session teardown

Compatibility behavior includes:

mcp-session-id
support for the configured native session header
SSE id
Last-Event-ID replay against a bounded buffer

Authorization Metadata

When OAuth is enabled, the server can expose:

authorization server metadata
protected resource metadata
authorization endpoint
token endpoint
registration endpoint
revocation endpoint

Use authorization_guide.md for deployment guidance and this document only for surface reference.

Notes On Parity

This document describes what the implementation exposes today. It does not claim that every edge case or experimental feature is fully exhausted. For the strict remaining gap list, use mcp_gap_todo.md.