config: [mcp] section with server definitions and disable gate

doc/plyngent.example.toml

@@ -26,6 +26,19 @@
 # [networking]
 # ssrf_assume_public_cidrs = ["198.18.0.0/15"]
 
+# MCP (Model Context Protocol) servers exposed as agent tools.
+# Defining a server opts it in; tools appear as mcp__<server>__<tool> with
+# LOCAL tags (confirm flow applies). Names in disable stay disconnected.
+# [mcp.servers.docs]
+# command = "npx"
+# args = ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"]
+# env = { RUST_LOG = "info" }
+# cwd = "/path"              # spawn working directory (empty = inherit)
+# timeout = 30.0             # per-request timeout (seconds)
+# read_only = true           # mark every tool READ_ONLY (eligible for /btw --tools=read)
+# [mcp]
+# disable = ["docs"]         # defined but never connected
+
 [agent]
 # Persona (omit → built-in coding-agent line). tool_directives is the tool playbook.
 # Override with multi-line literals (prefer ''' so nested " is fine):

src/plyngent/config/__init__.py

@@ -13,6 +13,8 @@ from .models import DatabaseConfig as DatabaseConfig
 from .models import DeepSeekConvention as DeepSeekConvention
 from .models import DeepseekProvider as DeepseekProvider
 from .models import HttpTimeoutConfig as HttpTimeoutConfig
+from .models import McpConfig as McpConfig
+from .models import McpServerConfig as McpServerConfig
 from .models import ModelConfig as ModelConfig
 from .models import NetworkingConfig as NetworkingConfig
 from .models import OpenAICompatibleProvider as OpenAICompatibleProvider

src/plyngent/config/models.py

@@ -143,6 +143,44 @@ class PluginsConfig(Struct, omit_defaults=True):
     disable: list[str] = field(default_factory=list)
 
 
+class McpServerConfig(Struct, omit_defaults=True):
+    """One MCP server definition (stdio transport today).
+
+    TOML example::
+
+        [mcp.servers.docs]
+        command = "npx"
+        args = ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"]
+        env = { RUST_LOG = "info" }
+        # cwd = "/path"            # spawn working directory (empty = inherit)
+        # timeout = 30.0            # per-request timeout in seconds
+        # read_only = true          # mark every tool READ_ONLY (safe side turns)
+
+    ``url`` is reserved for the streamable-HTTP transport; empty = stdio.
+    A defined server is connected unless its name appears in ``[mcp].disable``.
+    """
+
+    command: str = ""
+    args: list[str] = field(default_factory=list)
+    env: dict[str, str] = field(default_factory=dict)
+    cwd: str = ""
+    timeout: float = 30.0
+    read_only: bool = False
+    url: str = ""
+
+
+class McpConfig(Struct, omit_defaults=True):
+    """Model Context Protocol servers exposed as agent tools.
+
+    Defining a server under ``[mcp.servers.<name>]`` is the opt-in; tools are
+    namespaced ``mcp__<server>__<tool>`` and registered with LOCAL tags. Names
+    in ``disable`` stay disconnected even when defined.
+    """
+
+    servers: dict[str, McpServerConfig] = field(default_factory=dict)
+    disable: list[str] = field(default_factory=list)
+
+
 class NetworkingConfig(Struct, omit_defaults=True):
     """Host-side network policy for tools such as ``fetch``.
 

src/plyngent/config/store.py

@@ -9,6 +9,7 @@ import tomlkit
 from .models import (
     AgentConfig,
     DatabaseConfig,
+    McpConfig,
     ModelConfig,
     NetworkingConfig,
     PluginsConfig,
@@ -56,6 +57,29 @@ def _parse_networking(raw: dict[str, object]) -> NetworkingConfig:
         return NetworkingConfig()
 
 
+def _parse_mcp(raw: dict[str, object]) -> McpConfig:
+    """Parse the ``[mcp]`` section, falling back to defaults.
+
+    Unknown keys (typos like ``cmds``) are rejected the same way as providers:
+    a malformed section silently degrades to "no MCP servers" instead of a
+    half-parsed one.
+    """
+    try:
+        config = msgspec.convert(raw, McpConfig)
+    except msgspec.ValidationError:
+        return McpConfig()
+    known = {"servers", "disable"}
+    if set(raw) - known:
+        return McpConfig()
+    known_server = {"command", "args", "env", "cwd", "timeout", "read_only", "url"}
+    servers_raw = cast("dict[str, object]", raw.get("servers", {}))
+    for name, raw_entry in servers_raw.items():
+        entry = cast("dict[str, object]", raw_entry)
+        if not isinstance(raw_entry, dict) or not name.strip() or set(entry) - known_server:
+            return McpConfig()
+    return config
+
+
 def _parse_providers(
     document: tomlkit.TOMLDocument,
 ) -> tuple[dict[str, Provider], dict[str, object], dict[str, Provider]]:
@@ -125,6 +149,7 @@ class ConfigStore:
     _agent: AgentConfig
     _plugins: PluginsConfig
     _networking: NetworkingConfig
+    _mcp: McpConfig
     _providers: dict[str, Provider]
     _bad_providers: dict[str, object]
     _recoverable_providers: dict[str, Provider]
@@ -137,6 +162,7 @@ class ConfigStore:
         self._agent = _parse_agent(cast("dict[str, object]", raw.get("agent", {})))
         self._plugins = _parse_plugins(cast("dict[str, object]", raw.get("plugins", {})))
         self._networking = _parse_networking(cast("dict[str, object]", raw.get("networking", {})))
+        self._mcp = _parse_mcp(cast("dict[str, object]", raw.get("mcp", {})))
         self._providers, self._bad_providers, self._recoverable_providers = _parse_providers(document)
 
     @property
@@ -187,6 +213,13 @@ class ConfigStore:
         """Typed networking section (e.g. Fake-IP SSRF exemptions)."""
         return self._networking
 
+    # -- mcp (read-only) --
+
+    @property
+    def mcp_config(self) -> McpConfig:
+        """Typed MCP section (server definitions + disable list)."""
+        return self._mcp
+
     def set_plugins_enable(self, names: Sequence[str]) -> PluginsConfig:
         """Replace the plugin enable list (in-memory; call :meth:`write` to persist)."""
         cleaned = [name.strip() for name in names if name.strip()]
@@ -390,6 +423,7 @@ class ConfigStore:
         self._agent = _parse_agent(cast("dict[str, object]", raw.get("agent", {})))
         self._plugins = _parse_plugins(cast("dict[str, object]", raw.get("plugins", {})))
         self._networking = _parse_networking(cast("dict[str, object]", raw.get("networking", {})))
+        self._mcp = _parse_mcp(cast("dict[str, object]", raw.get("mcp", {})))
         self._providers, self._bad_providers, self._recoverable_providers = _parse_providers(self._document)
 
     # -- internal sync helpers --

tests/test_config/test_mcp_section.py

@@ -0,0 +1,66 @@
+"""[mcp] section parse: server definitions, disable gate, malformed fallback."""
+
+from __future__ import annotations
+
+from plyngent.config import load
+
+
+def test_mcp_defaults_and_parse(tmp_path) -> None:
+    path = tmp_path / "c.toml"
+    _ = path.write_text("", encoding="utf-8")
+    store = load(path)
+    assert store.mcp_config.servers == {}
+    assert store.mcp_config.disable == []
+
+    path.write_text(
+        """
+[mcp.servers.docs]
+command = "npx"
+args = ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"]
+env = { RUST_LOG = "info" }
+timeout = 10.0
+read_only = true
+
+[mcp.servers.search]
+command = "uvx"
+args = ["mcp-server-fetch"]
+
+[mcp]
+disable = ["search"]
+""",
+        encoding="utf-8",
+    )
+    store = load(path)
+    mcp = store.mcp_config
+    assert set(mcp.servers) == {"docs", "search"}
+    docs = mcp.servers["docs"]
+    assert docs.command == "npx"
+    assert docs.args == ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"]
+    assert docs.env == {"RUST_LOG": "info"}
+    assert docs.timeout == 10.0
+    assert docs.read_only is True
+    assert docs.url == ""
+    assert mcp.disable == ["search"]
+
+
+def test_mcp_malformed_section_falls_back_to_defaults(tmp_path) -> None:
+    path = tmp_path / "c.toml"
+    # Unknown section key.
+    path.write_text("[mcp]\nenabled = true\n", encoding="utf-8")
+    store = load(path)
+    assert store.mcp_config.servers == {}
+
+    # Unknown server key (typo).
+    path.write_text('[mcp.servers.docs]\ncmds = "npx"\n', encoding="utf-8")
+    store = load(path)
+    assert store.mcp_config.servers == {}
+
+    # Server entry is not a table.
+    path.write_text("[mcp]\nservers = 3\n", encoding="utf-8")
+    store = load(path)
+    assert store.mcp_config.servers == {}
+
+    # Empty server name.
+    path.write_text('[mcp.servers.""]\ncommand = "npx"\n', encoding="utf-8")
+    store = load(path)
+    assert store.mcp_config.servers == {}